Thermoplastic elastomer composition and process for producing same

ABSTRACT

A thermoplastic elastomer composition having excellent durability and flexibility while possessing superior air impermeability. In particular, a process for producing a thermoplastic elastomer composition having high rubber content by multistage addition of at least one vulcanizable rubber component, in which the time required to substantially cure the at least one rubber component preferably is less the mixer residence time. Such compositions are particularly useful in applications such as tire innerliners and barrier films or layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/US2005/038824, filed on Oct.27, 2005, the entire contents of all are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to thermoplastic elastomer compositionsparticularly useful for tire and other industrial rubber applicationsand to processes for producing such compositions.

BACKGROUND OF THE INVENTION

Thermoplastic elastomer compositions are particularly useful for tireand other industrial rubber applications. For example EP 0 722 850 B1discloses a low-permeability thermoplastic elastomer composition that issuperior as a gas-barrier layer in pneumatic tires. This thermoplasticelastomer composition comprises a low-permeability thermoplastic matrix,such as polyamide or a blend of polyamides, in which there is disperseda low-permeability rubber, such as brominatedpoly(isobutylene-co-paramethylstyrene). In EP 0 857 761 A1 and EP 0 969039 A1, the viscosity ratio of the thermoplastic matrix and thedispersed rubber phase was specified both as a function of the volumefraction ratio and, independently, to be close to a value of one inorder to produce a high concentration of small particle size vulcanizedrubber particles dispersed in a thermoplastic phase. EP 0 969 039 A1further discloses that small particle size rubber dispersed in athermoplastic resin matrix was important in order to achieve acceptabledurability of the resulting composition, particularly where suchcompositions are intended to be used as innerliners in pneumatic tires.

Compositions exhibiting low gas permeability performance (i.e.,functioning as a gas barrier) composed of thermoplasticresin/thermoplastic resin-based blends such as a high densitypolyethylene resin and nylon 6 or nylon 66 (HDPE/PA6.66), a polyethyleneterephthalate and aromatic nylon (PET/MXD6), a polyethyleneterephthalate and vinyl alcohol-ethylene copolymer (PET/EVOH), where onethermoplastic resin is layered over the other layer to form plurallayers by molding, and processes for producing the same, are disclosed,for example, by I. Hata, Kobunshi (Polymers), 40 (4), 244 (1991).Further, an application regarding the use of such a composition as theinnerliner layer of a tire is disclosed in Japanese Patent ApplicationNo. 7-55929. However, since these materials are thermoplasticresin/thermoplastic resin blends, while they are superior in gas barrierperformance, they lack flexibility, and therefore, such films are liableto break when the tire is in use.

Further, there are also examples of the use of a thermoplastic elastomercomposed of a rubber and a thermoplastic resin for use as an innerlineror in a tire; see, Japanese Patent Application No. 8-183683, but ingeneral, a flexible material of the type disclosed therein and havingsuperior durability has low heat resistance. With a thermoplasticelastomer using a thermoplastic resin having a melting point less thanthe tire vulcanization temperature as a matrix, when the tirevulcanization bladder is released at the end of the tire vulcanizationcycle, the tire inside surface is subject to appearance defects due tothe thermoplastic resin sticking to or rubbing with the bladder.

Control of the viscosity difference between the rubber and resin duringmixing in order to reduce the particle size of the dispersed rubber hasbeen reported by S. Wu, Polym. Eng. Sci., 27(5), 1987. Wu reported thatthe dispersed rubber particle size was reduced where the ratio of meltviscosities of the rubber/resin is brought close to 1, that is, nodifference in viscosities. However, it is reported in EP 0 969 039 A1that, in attempting to fabricate a thermoplastic elastomer compositionhaving sufficient flexibility, strength and elongation, as well assuperior durability, by increasing the rubber ratio, and keeping theratio of melt viscosities of the rubber/resin at 1, the rubber becomesthe matrix and the composition no longer exhibits thermoplasticity.

In Japanese Patent Application Nos. 8-193545, 9-175150, and 10-235386 itis proposed that, in a laminate structure in which dynamic fatigueresistance is required, such as tire or a hose, when using a gaspermeation preventive thermoplastic elastomer composition composed ofrubber/resin dispersed therein, it is known to obtain a balance betweenthe flexibility and gas permeation preventive property by making use ofa blend of flexible N11-nylon or N12-nylon and the superior gaspermeation preventive property of N6-nylon or N66-nylon. Further, it wasproposed to define volume fraction and melt viscosity using thefollowing equation:(φ_(d)/φ_(m))×(η_(m)/η_(d))<1.0wherein the volume fractions of the continuous phase component anddispersion phase component in the thermoplastic elastomer compositionare φ_(m) and φ_(d) and the melt viscosities of the components are η_(m)and η_(d) and further to bring the ratio of viscosities η_(m)/η_(d)close to 1 to reduce the dispersed rubber particle size domain toimprove the durability. However, it is reported in EP 0 969 039 A1 thatthe durability at low temperatures was insufficient by just reducing therubber particle size.

The limitations of the previous approaches to achieving improvedperformance of the desirable compositions comprising a small particlesize rubber domain dispersed in a thermoplastic matrix, the compositionexhibiting improved fluid (gas or liquid) barrier properties anddesirable levels of strength and durability suitable for use in tiresand hose applications has been accomplished by use of the processes ofthe present invention.

Other references of interest include: WO 2004/081107, WO 2004/081106, WO2004/081108, WO 2004/081116, WO 2004/081099, U.S. Pat. No. 4,480,074,U.S. Pat. No. 4,873,288, U.S. Pat. No. 5,073,597, U.S. Pat. No.5,157,081, U.S. Pat. No. 6,079,465, U.S. Pat. No. 6,346,571, and U.S.Pat. No. 6,538,066.

SUMMARY OF THE INVENTION

This invention relates to a thermoplastic elastomer compositioncomprising (A) at least one halogenated isobutylene-containingelastomer; and (B) at least one nylon resin having a melting point ofabout 170° C. to about 230° C.; wherein: (1) at least one halogenatedisobutylene-containing elastomer is present as a dispersed phase ofsmall vulcanized particles in a continuous phase of said nylon where theparticles have been formed by dynamic vulcanization and the particlescomprising greater than about 60 volume % of the volume of saidelastomer and said resin.

In a particularly preferred embodiment the invention is also directed toa process conducted in a suitable mixer for producing a thermoplasticelastomer composition, said mixer having a characteristic residencetime, said composition comprising greater than about 60 volume % ofdispersed particles of a total amount of at least one halogenatedisobutylene-containing elastomer, said particles dispersed in acontinuous thermoplastic nylon resin matrix, said process comprising thesteps of: (1) mixing halogenated elastomer-containing composition (A),said composition (A) comprising a first fraction of the total amount ofhalogenated elastomer in said thermoplastic elastomer composition andfurther comprising a cure system for said first elastomer fraction; andthermoplastic nylon resin (B) under suitable dynamic vulcanizationconditions of time, temperature and shear to form composition (C); (2)mixing composition (C) and halogenated elastomer-containing composition(D), said composition (D) comprising a second fraction of the totalamount of halogenated elastomer in said thermoplastic elastomercomposition and further comprising a cure system for said secondelastomer fraction; under suitable dynamic vulcanization conditions oftime, temperature and shear to form composition (E); (3) if the sum ofsaid first and second fractions of halogenated elastomer is less thanthe total amount of halogenated elastomer in said thermoplasticelastomer composition, mixing composition (E) and halogenatedelastomer-containing composition (F), said composition (F) comprising athird fraction of the total amount of halogenated elastomer in saidthermoplastic elastomer composition and further comprising a cure systemfor said third elastomer fraction; under suitable dynamic vulcanizationconditions of time, temperature and shear to form composition (G);wherein the step of dynamically vulcanizing a fractional additionalamount of halogenated elastomer in the presence of the dynamicallyvulcanized composition of the preceding step is repeated as many timesas necessary in order to obtain the total amount of halogenatedelastomer in said thermoplastic elastomer composition; and wherein eachsaid dynamic vulcanization conditions at each step are sufficient toeffect a cure state in said elastomer particles of at least about 50% ofthe maximum cure state for said elastomer and cure system and whereinsaid dynamic vulcanization time period is equal to or less than aboutthe characteristic residence time of said mixer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view of the microstructure according the embodiment ofExample 13, i.e., 20 microns×20 microns AFM image, wherein the lightphase: Nylon and dark phase: BIMS.

DETAILED DESCRIPTION

Preferred applications of the present invention relate to thermoplasticelastomer compositions for tire innerliner and barrier films, moreparticularly to thermoplastic elastomer compositions exhibitingexcellent durability and impermeability to fluids such as air as well asliquids. Preferred compositional features are directed to maximizedcontent of dispersed halogenated isobutylene elastomers in the form ofvulcanized particles dispersed in a polyamide thermoplastic matrix.Additionally, particularly preferred aspects of the invention relate toprocesses for producing a thermoplastic elastomer composition capable ofproviding a rubber domain comprising small sized particles while suchdomains are also highly extensible and elastic. Furthermore, theinvention includes processes for producing pneumatic tires and hosesusing the above compositions. The preferred elastomer exhibitslow-permeability and is preferably a polymer such as halogenatedisobutylene-containing elastomers and particularly preferred arebrominated elastomers, especially brominatedparamethylstyrene-co-isobutylene polymers (BIMS); preferred arebromobutyl elastomers exhibiting high content of the structureillustrated hereinafter below; and also preferred are commercialbromobutyl elastomers, or blends thereof with one or more of theaforementioned brominated elastomers with one another or with otherpolymers.

As used herein, the new numbering scheme for the Periodic Table Groupsis used as disclosed in CHEMICAL AND ENGINEERING NEWS, 63(5), 27 (1985).All molecular weights are weight average unless otherwise noted.

Throughout the entire specification, including the claims, the word“comprise” and variations of the word, such as “comprising” and“comprises,” as well as “have,” “having,” “includes,” “include” and“including,” and variations thereof, means that the named steps,elements or materials to which it refers are essential, but other steps,elements or materials may be added and still form a construct with thescope of the claim or disclosure. When recited in describing theinvention and in a claim, it means that the invention and what isclaimed is considered to what follows and potentially more. These terms,particularly when applied to claims, are inclusive or open-ended and donot exclude additional, unrecited elements or methods steps.

In the present context, “consisting essentially of” is meant to excludeany element or combination of elements, as well as any amount of anyelement or combination of elements, that would alter the basic and novelcharacteristics of the invention. Thus, by way of examples only, athermoplastic composition that is prepared by a method other than oneinvolving dynamic vulcanization or by use of a dynamic vulcanizationmethod in which all of the rubber component is added in a single amountor in which high diene rubber or other polymer or polymer combination isused to the exclusion of halogenated isobutylene-containing rubber insuch a composition, would be excluded. Alternatively, and again forexemplary purposes only, a thermoplastic composition in which the rubbercure system results in a cure time to achieve the necessary level ofcure state in the rubber that is substantially greater than theresidence time of the mixer used for conducting dynamic vulcanizationwould be excluded.

For purposes of the present invention, unless otherwise defined withrespect to a specific property, characteristic or variable, the term“substantially” as applied to any criteria, such as a property,characteristic or variable, means to meet the stated criteria in suchmeasure such that one skilled in the art would understand that thebenefit to be achieved, or the condition or property value desired ismet.

Polymer may be used to refer to homopolymers, copolymers, interpolymers,terpolymers, etc. Likewise, a copolymer may refer to a polymercomprising at least two monomers, optionally with other monomers.

When a polymer is referred to as comprising a monomer, the monomer ispresent in the polymer in the polymerized form of the monomer or in thederivative form the monomer. However, for ease of reference the phrase“comprising the (respective) monomer” or the like is used as shorthand.Likewise, when catalyst components are described as comprising neutralstable forms of the components, it is well understood by one skilled inthe art, that the active form of the component is the form that reactswith the monomers to produce polymers.

Isoolefin refers to any olefin monomer having two substitutions on thesame carbon.

Multiolefin refers to any monomer having two double bonds. In apreferred embodiment, the multiolefin is any monomer comprising twodouble bonds, preferably two conjugated double bonds such as aconjugated diene like isoprene.

Elastomer or elastomers as used herein, refers to any polymer orcomposition of polymers consistent with the ASTM D1566 definition. Theterms may be used interchangeably with the term “rubber(s).”

Alkyl refers to a paraffinic hydrocarbon group which may be derived froman alkane by dropping one or more hydrogens from the formula, such as,for example, a methyl group (CH₃), or an ethyl group (CH₃CH₂), etc.

Aryl refers to a hydrocarbon group that forms a ring structurecharacteristic of aromatic compounds such as, for example, benzene,naphthalene, phenanthrene, anthracene, etc., and typically possessalternate double bonding (“unsaturation”) within its structure. An arylgroup is thus a group derived from an aromatic compound by dropping oneor more hydrogens from the formula such as, for example, phenyl, orC₆H₅.

Substituted refers to at least one hydrogen group being replaced by atleast one substituent selected from, for example, halogen (chlorine,bromine, fluorine, or iodine), amino, nitro, sulfoxy (sulfonate or alkylsulfonate), thiol, alkylthiol, and hydroxy; alkyl, straight or branchedchain having 1 to 20 carbon atoms which includes methyl, ethyl, propyl,tert-butyl, isopropyl, isobutyl, etc.; alkoxy, straight or branchedchain alkoxy having 1 to 20 carbon atoms, and includes, for example,methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, secondarybutoxy, tertiary butoxy, pentyloxy, isopentyloxy, hexyloxy, heptyloxy,octyloxy, nonyloxy, and decyloxy; haloalkyl, which means straight orbranched chain alkyl having 1 to 20 carbon atoms which contains at leastone halogen, and includes, for example, chloromethyl, bromomethyl,fluoromethyl, iodomethyl, 2-chloroethyl, 2-bromoethyl, 2-fluoroethyl,3-chloropropyl, 3-bromopropyl, 3-fluoropropyl, 4-chlorobutyl,4-fluorobutyl, dichloromethyl, dibromomethyl, difluoromethyl,diiodomethyl, 2,2-dichloroethyl, 2,2-dibromomethyl, 2,2-difluoroethyl,3,3-dichloropropyl, 3,3-difluoropropyl, 4,4-dichlorobutyl,4,4-difluorobutyl, trichloromethyl, 4,4-difluorobutyl, trichloromethyl,trifluoromethyl, 2,2,2-trifluoroethyl, 2,3,3-trifluoropropyl,1,1,2,2-tetrafluoroethyl, and 2,2,3,3-tetrafluoropropyl. Thus, forexample, a “substituted styrenic unit” includes p-methylstyrene,p-ethylstyrene, etc.

The present invention comprises at least one halogenatedisobutylene-containing rubber. Typically, it is present in a compositionwith a thermoplastic engineering resin (preferably nylon) as describedherein, in a volume ratio of rubber to resin of about 50/45 to 80/20;preferably about 60/40 to about 75/25; more preferably about 65/35 toabout 75/25. Halogenated rubber is defined as a rubber having at leastabout 0.1 mole % halogen, such halogen selected from the groupconsisting of bromine, chlorine and iodine. Preferred halogenatedrubbers useful in this invention include halogenated isobutylenecontaining elastomers (also referred to as halogenated isobutylene-basedhomopolymers or copolymers) These elastomers can be described as randomcopolymer of a C₄ to C₇ isomonoolefin derived unit, such as isobutylenederived unit, and at least one other polymerizable unit. In oneembodiment of the invention, the halogenated isobutylene-based copolymeris a butyl-type rubber or branched butyl-type rubber, especiallybrominated versions of these elastomers. (Useful unsaturated butylrubbers such as homopolymers and copolymers of olefins or isoolefins andother types of elastomers suitable for the invention are well known andare described in RUBBER TECHNOLOGY 209-581 (Maurice Morton ed., Chapman& Hall 1995), THE VANDERBILT RUBBER HANDBOOK 105-122 (Robert F. Ohm ed.,R.T. Vanderbilt Co., Inc. 1990), and Edward Kresge and H. C. Wang in 8KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY 934-955 (John Wiley &Sons, Inc. 4th ed. 1993)).

Butyl rubbers are typically prepared by reacting a mixture of monomers,the mixture having at least (1) a C₄ to C₁₂ isoolefin monomer componentsuch as isobutylene with (2) a multiolefin, monomer component. Theisoolefin is in a range from 70 to 99.5 wt % by weight of the totalmonomer mixture in one embodiment, and 85 to 99.5 wt % in anotherembodiment. The multiolefin component is present in the monomer mixturefrom 30 to 0.5 wt % in one embodiment, and from 15 to 0.5 wt % inanother embodiment. In yet another embodiment, from 8 to 0.5 wt % of themonomer mixture is multiolefin. The isoolefin is preferably a C₄ to C₁₂compound, non-limiting examples of which are compounds such asisobutylene, isobutene, 2-methyl-1-butene, 3-methyl-1-butene,2-methyl-2-butene, 1-butene, 2-butene, methyl vinyl ether, indene,vinyltrimethylsilane, hexene, and 4-methyl-1-pentene. The multiolefin isa C₄ to C₁₄ multiolefin such as isoprene, butadiene,2,3-dimethyl-1,3-butadiene, myrcene, 6,6-dimethyl-fulvene, hexadiene,cyclopentadiene, and piperylene, and other monomers such as disclosed inEP 0 279 456 and U.S. Pat. Nos. 5,506,316 and 5,162,425. Otherpolymerizable monomers such as styrene and dichlorostyrene are alsosuitable for homopolymerization or copolymerization in butyl rubbers.One embodiment of the butyl rubber polymer useful in the invention isobtained by reacting 95 to 99.5 wt % of isobutylene with 0.5 to 8 wt %isoprene, or from 0.5 wt % to 5.0 wt % isoprene in yet anotherembodiment. Butyl rubbers and methods of their production are describedin detail in, for example, U.S. Pat. Nos. 2,356,128, 3,968,076,4,474,924, 4,068,051 and 5,532,312.

Halogenated butyl rubber is produced by the halogenation of the butylrubber product described above. Halogenation can be carried out by anymeans, and the invention is not herein limited by the halogenationprocess. Methods of halogenating polymers such as butyl polymers aredisclosed in U.S. Pat. Nos. 2,631,984, 3,099,644, 4,288,575, 4,554,326,4,632,963, 4,681,921, 4,650,831, 4,384,072, 4,513,116 and 5,681,901. Inone embodiment, the butyl rubber is halogenated in hexane diluent atfrom 4 to 60 (C using bromine (Br₂) or chlorine (Cl₂) as thehalogenation agent. Post-treated halogenated butyl rubber can also beused, as disclosed in U.S. Pat. No. 4,288,575. Useful halogenated butylrubber typically has a Mooney Viscosity of about 20 to about 70 (ML 1+8at 125 (C); for example, and about 25 to about 55 in another embodiment.The preferred halogen content is typically about 0.1 to 10 wt % based onthe weight of the halogenated rubber; for example, about 0.5 to 5 wt %;alternatively, about 0.8 to about 2.5 wt %; for example, about 1 toabout 2 wt %. A particularly preferred form of halogenated butyl rubbercontains a high content of the following halogenated structure(preferably 60 to 95% as measured by NMR) where X represents the halogenand, in a particularly preferred embodiment, the halogen is bromine;alternatively the halogen is chlorine:

A commercial embodiment of a halogenated butyl rubber useful in thepresent invention is Bromobutyl 2222 (ExxonMobil Chemical Company). ItsMooney Viscosity is typically about 27 to 37 (ML 1+8 at 125 (C, ASTM1646, modified), and its bromine content is about 1.8 to 2.2 wt %relative to the Bromobutyl 2222. Furthermore, the cure characteristicsof Bromobutyl 2222 as provided by the manufacturer are as follows: MHabout 28 to 40 dN m, ML is about 7 to 18 dN m (ASTM D2084). Anothercommercial embodiment of the halogenated butyl rubber useful in thepresent invention is Bromobutyl 2255 (ExxonMobil Chemical Company). ItsMooney Viscosity is about 41 to 51 (ML 1+8 at 125 (C, ASTM D1646), andits bromine content is about 1.8 to 2.2 wt %. Furthermore, its curecharacteristics as disclosed by the manufacturer are as follows: MH isfrom 34 to 48 dN m, ML is from 11 to 21 dN m (ASTM D2084). Commercialisobutylene polymers are described in detail by R. N. Webb, T. D.Shaffer and A. H. Tsou, “Commercial Isobutylene Polymers,” Encyclopediaof Polymer Science and Technology, 2002, John Wiley & Sons, incorporatedherein by reference.

Another useful embodiment of halogenated butyl rubber is halogenated,branched or “star-branched” butyl rubber. These rubbers are describedin, for example, EP 0 678 529 B1, U.S. Pat. Nos. 5,182,333 and5,071,913, each incorporated herein by reference. In one embodiment, thestar-branched butyl rubber (“SBB”) is a composition comprising butylrubber and a polydiene or block copolymer. For purposes of the presentinvention, the method of forming the SBB is not a limitation. Thepolydienes, block copolymer, or branching agents (hereinafter“polydienes”), are typically cationically reactive and are presentduring the polymerization of the butyl or halogenated butyl rubber, orcan be blended with the butyl rubber to form the SBB. The branchingagent or polydiene can be any suitable branching agent, and theinvention is not limited to the type of polydiene or branching agentused to make the SBB.

In one embodiment, the SBB is a composition of butyl or halogenatedbutyl rubber as described above and a copolymer of a polydiene and apartially hydrogenated polydiene selected from the group consisting ofstyrene, polybutadiene, polyisoprene, polypiperylene, natural rubber,styrene-butadiene rubber, ethylene-propylene diene rubber (EPDM),ethylene-propylene rubber (EPM), styrene-butadiene-styrene andstyrene-isoprene-styrene block copolymers. Polydienes can be present,based on the total monomer content in wt %, typically greater than 0.3wt %; alternatively, about 0.3 to about 3 wt %; or about 0.4 to 2.7 wt%.

Preferably the branched or “star-branched” butyl rubber used herein ishalogenated. In one embodiment, the halogenated star-branched butylrubber (“HSBB”) comprises a butyl rubber, either halogenated or not, anda polydiene or block copolymer, either halogenated or not. Thehalogenation process is described in detail in U.S. Pat. No. 4,074,035,U.S. Pat. No. 5,071,913, U.S. Pat. No. 5,286,804, U.S. Pat. No.5,182,333 and U.S. Pat. No. 6,228,978. The present invention is notlimited by the method of forming the HSBB. The polydiene/blockcopolymer, or branching agents (hereinafter “polydienes”), are typicallycationically reactive and are present during the polymerization of thebutyl or halogenated butyl rubber, or can be blended with the butyl orhalogenated butyl rubber to form the HSBB. The branching agent orpolydiene can be any suitable branching agent, and the invention is notlimited by the type of polydiene used to make the HSBB.

In one embodiment, the HSBB is typically a composition comprisinghalogenated butyl rubber as described above and a copolymer of apolydiene and a partially hydrogenated polydiene selected from the groupconsisting of styrene, polybutadiene, polyisoprene, polypiperylene,natural rubber, styrene-butadiene rubber, ethylene-propylene dienerubber, styrene-butadiene-styrene and styrene-isoprene-styrene blockcopolymers. Polydienes can be present, based on the total monomercontent in wt %, typically greater than about 0.3 wt %, alternativelyabout 0.3 to 3 wt %, or about 0.4 to 2.7 wt %.

A commercial embodiment of HSBB useful in the present invention isBromobutyl 6222 (ExxonMobil Chemical Company), having a Mooney Viscosity(ML 1+8 at 125° C., ASTM D1646) of about 27 to 37, and a bromine contentof about 2.2 to 2.6 wt %. Further, cure characteristics of Bromobutyl6222, as disclosed by the manufacturer, are as follows: MH is from 24 to38 dN·m, ML is from 6 to 16 dN·m (ASTM D2084).

Preferred isoolefin/para-alkylstyrene copolymers useful herein includerandom copolymers comprising a C₄ to C₇ isoolefin, such as isobutylene,and a halomethylstyrene. The halomethylstyrene may be an ortho-, meta-,or para-alkyl-substituted styrene. In one embodiment, thehalomethylstyrene is a p-halomethylstyrene containing at least 80%, morepreferably at least 90% by weight of the para-isomer. The “halo” groupcan be any halogen, desirably chlorine or bromine. The copolymer mayalso include functionalized interpolymers wherein at least some of thealkyl substituent groups present on the styrene monomer units containbenzylic halogen or another functional group described further below.These interpolymers are herein referred to as “isoolefin copolymerscomprising a halomethylstyrene” or simply “isoolefin copolymer.”

Preferred isoolefin copolymers can include monomers selected from thegroup consisting of isobutylene or isobutene, 2-methyl-1-butene,3-methyl-1-butene, 2 methyl-2-butene, 1-butene, 2-butene, methyl vinylether, indene, vinyltrimethylsilane, hexene, and 4-methyl-1-pentene.Preferred isoolefin copolymers may also further comprise multiolefins,preferably a C₄ to C₁₄ multiolefin such as isoprene, butadiene,2,3-dimethyl-1,3-butadiene, myrcene, 6,6-dimethyl-fulvene, hexadiene,cyclopentadiene, and piperylene, and other monomers such as disclosed inEP 279456 and U.S. Pat. No. 5,506,316 and U.S. Pat. No. 5,162,425.Desirable styrenic monomers in the isoolefin copolymer include styrene,methylstyrene, chlorostyrene, methoxystyrene, indene and indenederivatives, and combinations thereof.

Preferred isoolefin copolymers may be characterized as interpolymerscontaining the following monomer units randomly spaced along the polymerchain:

wherein R and R¹ are independently hydrogen, lower alkyl, preferably C₁to C₇ alkyl and primary or secondary alkyl halides and X is a functionalgroup such as halogen. Desirable halogens are chlorine, bromine orcombinations thereof, preferably bromine. Preferably R and R¹ are eachhydrogen. The —CRR₁H and —CRR₁X groups can be substituted on the styrenering in either the ortho, meta, or para positions, preferably the paraposition. Up to 60 mole % of the p-substituted styrene present in theinterpolymer structure may be the functionalized structure (2) above inone embodiment, and in another embodiment from 0.1 to 5 mol %. In yetanother embodiment, the amount of functionalized structure (2) is from0.4 to 1 mol %. The functional group X may be halogen or some otherfunctional group which may be incorporated by nucleophilic substitutionof benzylic halogen with other groups such as carboxylic acids; carboxysalts; carboxy esters, amides and imides; hydroxy; alkoxide; phenoxide;thiolate; thioether; xanthate; cyanide; cyanate; amino and mixturesthereof. These functionalized isomonoolefin copolymers, their method ofpreparation, methods of functionalization and cure are more particularlydisclosed in U.S. Pat. No. 5,162,445.

Particularly useful of such copolymers of isobutylene andp-methylstyrene are those containing from 0.5 to 20 mole %p-methylstyrene wherein up to 60 mole % of the methyl substituent groupspresent on the benzyl ring contain a bromine or chlorine atom,preferably a bromine atom (p-bromomethylstyrene), as well as acid orester functionalized versions thereof wherein the halogen atom has beendisplaced by maleic anhydride or by acrylic or methacrylic acidfunctionality. These interpolymers are termed “halogenatedpoly(isobutylene-co-p-methylstyrene)” or “brominatedpoly(isobutylene-co-p-methylstyrene)”, and are commercially availableunder the name EXXPRO™ Elastomers (ExxonMobil Chemical Company, HoustonTex.). It is understood that the use of the terms “halogenated” or“brominated” are not limited to the method of halogenation of thecopolymer, but merely descriptive of the copolymer which comprises theisobutylene derived units, the p-methylstyrene derived units, and thep-halomethylstyrene derived units.

These functionalized polymers preferably have a substantiallyhomogeneous compositional distribution such that at least 95% by weightof the polymer has a p-alkylstyrene content within 10% of the averagep-alkylstyrene content of the polymer as measured by gel permeationchromatography (as shown in U.S. Pat. No. 5,162,445). More preferredpolymers are also characterized by a narrow molecular weightdistribution (Mw/Mn) of less than 5, more preferably less than 2.5, apreferred viscosity average molecular weight in the range of about200,000 to about 2,000,000 and a preferred number average molecularweight in the range of about 25,000 to about 750,000 as determined bygel permeation chromatography.

Preferred halogenated poly(isobutylene-co-p-methylstyrene) polymers arebrominated polymers which generally contain from about 0.1 to about 5 wt% of bromomethyl groups. In yet another embodiment, the amount ofbromomethyl groups is about 0.2 to about 2.5 wt %. Expressed anotherway, preferred copolymers contain about 0.05 to about 2.5 mole % ofbromine, based on the weight of the polymer, more preferably about 0.1to about 1.25 mole % bromine, and are substantially free of ring halogenor halogen in the polymer backbone chain. In one embodiment of theinvention, the interpolymer is a copolymer of C₄ to C₇ isomonoolefinderived units, p-methylstyrene derived units and p-halomethylstyrenederived units, wherein the p-halomethylstyrene units are present in theinterpolymer from about 0.4 to about 1 mol % based on the interpolymer.In another embodiment, the p-halomethylstyrene is p-bromomethylstyrene.The Mooney Viscosity (1+8, 125° C., ASTM D1646) is about 30 to about 60Mooney units.

In another embodiment, the relationship between the triad fraction of anisoolefin and a p-alkylstyrene and the mol % of p-alkylstyreneincorporated into the copolymer is described by the copolymer sequencedistribution equation described below and is characterized by thecopolymer sequence distribution parameter, m.F=1−{mA/(1+mA)}

-   -   where: m is the copolymer sequence distribution parameter,    -   A is the molar ratio of p-alkylstyrene to isoolefin in the        copolymer and,    -   F is the p-alkylstyrene-isoolefin-p-alkylstyrene triad fraction        in the copolymer.        The best fit of this equation yields the value of m for        copolymerization of the isoolefin and p-alkylstyrene in a        particular diluent. In certain embodiments, m is from less than        38; alternatively, from less than 36; alternatively, from less        than 35; and alternatively, from less than 30. In other        embodiments, m is from 1-38; alternatively, from 1-36;        alternatively, from 1-35; and alternatively from 1-30.        Copolymers having such characteristics are disclosed in WO        2004058825 and WO 2004058835.

In another embodiment, the isoolefin/para-alkylstyrene copolymer issubstantially free of long chain branching. For the purposes of thisinvention, a polymer that is substantially free of long chain branchingis defined to be a polymer for which g′_(vis.avg.) is determined to begreater than or equal to 0.978, alternatively, greater than or equal to0.980, alternatively, greater than or equal to 0.985, alternatively,greater than or equal to 0.990, alternatively, greater than or equal to0.995, alternatively, greater than or equal to 0.998, alternatively,greater than or equal to 0.999, as determined by triple detection sizeexclusion chromatography (SEC) as described below. Such polymers arealso disclosed in WO 2004058825 and WO 2004058835.

In another embodiment, the relationship between the triad fraction of anisoolefin and a multiolefin and the mol % of multiolefin incorporatedinto the halogenated rubber copolymer is described by the copolymersequence distribution equation below and is characterized by thecopolymer sequence distribution parameter, m.F=mA/(1+mA)²

-   -   where: m is the copolymer sequence distribution parameter,    -   A is the molar ratio of multiolefin to isoolefin in the        copolymer and,    -   F is the isoolefin-multiolefin-multiolefin triad fraction in the        copolymer.        Measurement of triad fraction of an isoolefin and a multiolefin        and the mol % of multiolefin incorporated into the copolymer is        described below. The best fit of this equation yields the value        of m for copolymerization of the isoolefin and multiolefin in        each diluent. In certain embodiments, m is from greater than        1.5; alternatively, from greater than 2.0; alternatively, from        greater than 2.5; alternatively, from greater than 3.0; and        alternatively, from greater than 3.5. In other embodiments, m is        from 1.10 to 1.25; alternatively, from 1.15 to 1.20;        alternatively, from 1.15 to 1.25; and alternatively, m is about        1.20. Halogenated rubbers that have these characteristics are        disclosed in WO 2004058825 and WO 2004058835.

In another embodiment, the halogenated rubber is substantially free oflong chain branching. For the purposes of this invention, a polymer thatis substantially free of long chain branching is defined to be a polymerfor which g′_(vis.avg.) is determined to be greater than or equal to0.978, alternatively, greater than or equal to 0.980, alternatively,greater than or equal to 0.985, alternatively, greater than or equal to0.990, alternatively, greater than or equal to 0.995, alternatively,greater than or equal to 0.998, alternatively, greater than or equal to0.999, as determined by triple detection SEC as follows. The presence orabsence of long chain branching in the polymers is determined usingtriple detection SEC. Triple detection SEC is performed on a Waters(Milford, Mass.) 150 C chromatograph operated at 40° C. equipped aPrecision Detectors (Bellingham, Mass.) PD2040 light scatteringdetector, a Viscotek (Houston, Tex.) Model 150R viscometry detector anda Waters differential refractive index detector (integral with the 150C). The detectors are connected in series with the light scatteringdetector being first, the viscometry detector second and thedifferential refractive index detector third. Tetrahydrofuran is used asthe eluent (0.5 ml/min.) with a set of three Polymer Laboratories, Ltd.(Shropshire, United Kingdom) 10 micron mixed-B/LS GPC columns. Theinstrument is calibrated against 16 narrow polystyrene standards(Polymer Laboratories, Ltd.). Data is acquired with TriSEC software(Viscotek) and imported into WaveMetric's Igor Pro program (Lake Oswego,Oreg.) for analysis. Linear polyisobutylene is used to establish therelationship between the intrinsic viscosity [η]_(linear) determined bythe viscometry detector) and the molecular weight (M_(w), determined bythe light scattering detector). The relationship between [η]_(linear)and M_(w) is expressed by the Mark-Houwink equation.[η]_(linear)=KM_(w) ^(α)Parameters K and α are obtained from the double-logarithmic plot ofintrinsic viscosity against M_(w), α is the slope, K the intercept.Significant deviations from the relationship established for the linearstandards indicate the presence of long chain branching. Generally,samples which exhibit more significant deviation from the linearrelationship contain more significant long chain branching. The scalingfactor g′ also indicates deviations from the determined linearrelationship.[η]_(sample)=g′[η]_(linear)The value of g′ is defined to be less than or equal to one and greaterthan or equal to zero. When g′ is equal or nearly equal to one, thepolymer is considered to be linear. When g′ is significantly less thanone, the sample is long chain branched. See e.g. E. F. Casassa and G. C.Berry in “Comprehensive Polymer Science,” Vol. 2, (71-120) G. Allen andJ. C. Bevington, Ed., Pergamon Press, New York, 1988. In tripledetection SEC, a g′ is calculated for each data slice of thechromatographic curve. A viscosity average g′ or g′_(vis.avg.) iscalculated across the entire molecular weight distribution. The scalingfactor g′_(vis.avg.) is calculated from the average intrinsic viscosityof the sample:g′ _(vis.avg.)=[η]_(avg.)/(KM _(w) ^(α)))Other preferred halogenated elastomers or rubbers include halogenatedisobutylene-p-methylstyrene-isoprene copolymer as described in WO01/21672A1.

The isobutylene-containing elastomers used in the thermoplasticelastomer compositions useful as fluid permeation prevention layer asdescribed herein may be the same or different as halogen containingelastomers present in other layers of the article being manufactured.For example if the fluid permeation layer is present as a tireinnerlayer, then the other layers of the tire, particularly those incontact with the innerlayer may also contain the sameisobutylene-containing elastomers. Likewise, the halogenated isobutylenecontaining elastomer useful in the air permeation prevention layer andthe elastomer useful in a tie layer, adhesive layer, and/or carcass maybe the same or different elastomer. In a preferred embodiment, thehalogenated isobutylene containing elastomer present in the airpermeation prevention layer and the elastomer present in the tie layer,adhesive layer, and/or carcass are the same elastomer. In anotherembodiment, they are different. By same is meant that the elastomershave comonomer and halogen content within 2 weight % of each other,respectively. By different is meant that the elastomers comprisedifferent halogens or comonomers or that the elastomers have comonomeror halogen contents that are not within 2 weight % of each other. Forexample a BIMS copolymer having 3 weight % para-methyl styrene (PMS) and5 weight % bromine is considered different from a BIMS copolymer having11 weight % PMS and 5 weight % bromine. In a preferred embodiment, theelastomer present in the air permeation prevention layer is a brominatedcopolymer of isobutylene and para-methyl styrene and the halogenatedisobutylene containing elastomer present in the tie layer, adhesivelayer, and/or carcass is the same or a different brominated copolymer ofisobutylene and para-methyl styrene. In another embodiment, theelastomer present in the air permeation prevention layer is a brominatedcopolymer of isobutylene and para-methyl styrene and the halogenatedisobutylene containing elastomer present in the tie layer, adhesivelayer, and/or carcass is a brominated butyl rubber.

Useful DVA compositions described herein also comprise a thermoplasticor engineering resin (such as nylon) in addition to the elastomer.

For purposes of the present invention, an engineering resin (also calledan “engineering thermoplastic resin,” a “thermoplastic resin,” or a“thermoplastic engineering resin”) is defined to be any thermoplasticpolymer, copolymer or mixture thereof having a Young's modulus of morethan 500 MPa and, preferably, an air permeation coefficient of less than60×10⁻¹² cc cm/cm² sec cm Hg (at 30° C.), and, preferably, a meltingpoint of about 170° C. to about 230° C., including, but not limited to,one or more of the following:

-   -   a) polyamide resins: nylon 6 (N6), nylon 66 (N66), nylon 46        (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon        612 (N612), nylon 6/66 copolymer (N6/66), nylon 6/66/610        (N6/66/610), nylon MXD6 (MXD6), nylon 6T (N6T), nylon 6/6T        copolymer, nylon 66/PP copolymer, nylon 66/PPS copolymer;    -   b) polyester resins: polybutylene terephthalate (PBT),        polyethylene terephthalate (PET), polyethylene isophthalate        (PEI), PET/PEI copolymer, polyacrylate (PAR), polybutylene        naphthalate (PBN), liquid crystal polyester, polyoxalkylene        diimide diacid/polybutyrate terephthalate copolymer and other        aromatic polyesters;    -   c) polynitrile resins: polyacrylonitrile (PAN),        polymethacrylonitrile, acrylonitrile-styrene copolymers (AS),        methacrylonitrile-styrene copolymers,        methacrylonitrile-styrene-butadiene copolymers;    -   d) polymethacrylate resins: polymethyl methacrylate,        polyethylacrylate;    -   e) polyvinyl resins (for illustration, not limitation: vinyl        acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol/ethylene        copolymer (EVOA), polyvinylidene chloride (PVDC), polyvinyl        chloride (PVC), polyvinyl/polyvinylidene copolymer,        polyvinylidene chloride/methacrylate copolymer;    -   f) cellulose resins: cellulose acetate, cellulose acetate        butyrate;    -   g) fluorine resins: polyvinylidene fluoride (PVDF), polyvinyl        fluoride (PVF), polychlorofluoroethylene (PCTFE),        tetrafluoroethylene/ethylene copolymer (ETFE);    -   h) polyimide resins: aromatic polyimides);    -   i) polysulfones;    -   j) polyacetals;    -   k) polyactones;    -   l) polyphenylene oxide and polyphenylene sulfide;    -   m) styrene-maleic anhydride;    -   n) aromatic polyketones; and    -   o) mixtures of any and all of a) through n) inclusive as well as        mixtures of any of the illustrative or exemplified engineering        resins within each of a) through n) inclusive.

For purposes of the present invention, this definition of engineeringresin excludes polymers of olefins, such as polyethylene andpolypropylene.

Preferred engineering resins include polyamide resins and mixturesthereof; particularly preferred resins include Nylon 6, Nylon 6/66copolymer, Nylon 11, Nylon 12, Nylon 610, Nylon 612 and their blends.According to an alternative preferred embodiment of the presentinvention, the thermoplastic elastomer composition may be formulatedusing a thermoplastic resin component where the nylon resin component iscomprises nylon 11 or nylon 12, and nylon 6/66 copolymer in a ratio ofcomposition (ratio by weight) of about 10/90 to about 90/10; preferablyabout 30/70 to about 85/15. Such a thermoplastic elastomer compositionbased on blended resins can provide a thermoplastic elastomercomposition having superior durability and appearance, e.g., of thecured surface of a tire innerliner as well as superior air retentionproperties, as well as demonstrating a good balance of these properties.

Optionally, other rubbers or elastomers can be used in combination withthe halogenated isobutylene-containing elastomer. Such an optionalrubber component includes high diene rubbers and their hydrates. Highdiene content rubbers or elastomers are also referred to as high dienemonomer rubber. It is typically a rubber comprising typically at least50 mole % of a C₄-C₁₂ diene monomer, typically at least about 60 mole %to about 100 mole %; more preferably at least about 70 mole % to about100 mole %; more preferably at least about 80 mole % to about 100 mole%. Useful high diene monomer rubbers include homopolymers and copolymersof olefins or isoolefins and multiolefins, or homopolymers ofmultiolefins. These are well known and are described in RUBBERTECHNOLOGY, 179-374 (Maurice Morton ed., Chapman & Hall 1995), and THEVANDERBILT RUBBER HANDBOOK 22-80 (Robert F. Ohm ed., R.T. VanderbiltCo., Inc. 1990). Generally, other optional rubbers useful in the presentinvention include, for example natural rubber (NR), isoprene rubber(IR), epoxylated natural rubber, styrene butadiene rubber (SBR),polybutadiene rubber (BR) (including high cis BR and low cis BR),nitrile butadiene rubber (NBR), hydrogenated NBR, hydrogenated SBRolefin rubbers (for example, ethylene propylene rubbers (including bothEPDM and EPM), maleic acid-modified ethylene propylene rubbers (M-EPM),butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomercopolymers, acrylic rubbers (ACM), ionomers, other halogen-containingrubbers (for example, chloroprene rubbers (CR), hydrin rubbers (CHR),chlorosulfonated polyethylenes (CSM), chlorinated polyethylenes (CM),maleic acid-modified chlorinated polyethylenes (M-CM)), silicone rubbers(for example, methylvinyl silicone rubbers, dimethyl silicone rubbers,methylphenylvinyl silicone rubbers), sulfur-containing rubbers (forexample, polysulfide rubbers), fluoro rubbers (for example, vinylidenefluoride rubbers, fluorine-containing vinyl ether-based rubbers,tetrafluoroethylene-propylene rubbers, fluorine-containing siliconerubbers, fluorine-containing phosphagen rubbers), thermoplasticelastomers (for example, styrene-containing elastomers, olefinelastomers, ester elastomers, urethane elastomers, or polyamideelastomers), and their mixtures.

Preferred examples of high diene monomer rubbers include polyisoprene,polybutadiene rubber, styrene-butadiene rubber, natural rubber,chloroprene rubber, acrylonitrile-butadiene rubber and the like, whichmay be used alone or in combination and mixtures.

Since the thermoplastic engineering resin and the halogenatedisobutylene-containing rubber differ significantly in solubility, afurther optional compatibilizing ingredient may be useful for thepurposes of enhancing compatibility of these polymers. Suchcompatibilizers include ethylenically unsaturated nitrile-conjugateddiene-based high saturation copolymer rubbers (HNBR), epoxylated naturalrubbers (ENR), NBR, hydrin rubbers, acryl rubbers and mixtures thereof.Compatibilizers are thought to function by modifying, in particularreducing, the surface tension between the rubber and resin components.Other compatibilizers include copolymers such as those having thestructure of both or one of the thermoplastic resin and rubber polymeror a structure of a copolymer having an epoxy group, carbonyl group,halogen group, amine group, maleated group, oxazoline group, hydroxygroup, etc. capable of reacting with the thermoplastic resin or rubberpolymer. These may be selected based upon the type of the thermoplasticresin polymer and rubber polymer to be mixed, but useful copolymerstypically include, e.g., a styrene/ethylene-butylene/styrene blockcopolymer (SEBS) and its maleic acid-modified form; EPDM, EPDM/styrene,or EPDM/acrylonitrile graft copolymer and their maleic acid-modifiedforms; styrene/maleic acid copolymer; reactive phenoxy thermoplasticresin; and their mixtures. The amount of the compatibilizer blended isnot particularly limited, but, when used, typically is about 0.5 toabout 10 parts by weight, based upon 100 parts by weight of the polymercomponent, in other words, the total of the thermoplastic engineeringresin polymer and rubber polymer.

With reference to the polymers and/or elastomers referred to herein, theterms “cured,” “vulcanized,” or “crosslinked” refer to the chemicalreaction comprising forming bonds as, for example, during chainextension, or crosslinks between polymer chains comprising the polymeror elastomer to the extent that the elastomer undergoing such a processcan provide the necessary functional properties resulting from thecuring reaction when the tire is put to use. For purposes of the presentinvention, absolute completion of such curing reactions is not requiredfor the elastomer-containing composition to be considered “cured,”“vulcanized” or “crosslinked.” For example, for purposes of the presentinvention, a tire comprising an innerliner layer composition based onthe present invention is sufficiently cured when the tire of which it isa component passes the necessary product specification tests during andafter manufacturing and performs satisfactorily when used on a vehicle.Furthermore, the composition is satisfactorily, sufficiently orsubstantially cured, vulcanized or crosslinked when the tire can be putto use even if additional curing time could produce additionalcrosslinks.

Generally, polymer compositions, e.g., those used to produce tires, arecrosslinked in the finished tire product. Crosslinking or vulcanizationis accomplished by incorporation of curing agents and/or accelerators;the overall mixture of such agents being typically referred to as a cure“system.” It is known that the physical properties, performancecharacteristics, and durability of vulcanized rubber compounds aredirectly related to the number (crosslink density) and types ofcrosslinks formed during the vulcanization reaction. (See, e.g., Helt etal., The Post Vulcanization Stabilization for NR, RUBBER WORLD 18-23(1991). Curing agents include those components described above thatfacilitate or influence the cure of elastomers, and generally includemetals, metal oxides, accelerators, sulfur, peroxides, and other agentscommon in the art, and as described above. Crosslinking or curing agentsinclude at least one of, e.g., sulfur, zinc oxide, and fatty acids andmixtures thereof. Peroxide-containing cure systems may also be used.Generally, polymer compositions may be crosslinked by adding curativeagents, for example sulfur, metal oxides (i.e., zinc oxide, ZnO),organometallic compounds, radical initiators, etc. and heating thecomposition or mixture.

When the method known as “dynamic vulcanization” is used, the process ofdispersing the cure system is modified as described in detailhereinafter. Generally, the term “dynamic vulcanization” is used todenote a vulcanization process in which a thermoplastic or engineeringresin and at least one vulcanizable rubber are mixed under conditions ofhigh shear and elevated temperature in the presence of a curing agent orcuring system for the rubber(s). As a result, the rubber issimultaneously crosslinked and dispersed as particles, preferably in theform of a microgel, within the resin which forms a continuous matrix.The resulting composition is known in the art as a “dynamicallyvulcanized alloy” or DVA. Typically, dynamic vulcanization is effectedby mixing the ingredients at a temperature which is at or above thecuring temperature of the rubber, and at or above the meltingtemperature of the thermoplastic resin, using equipment such as rollmills, Banbury® mixers, continuous mixers, kneaders, or mixing extruders(such as twin screw extruders). The unique characteristic of thedynamically vulcanized or cured composition is that, notwithstanding thefact that the rubber is cured the composition can be processed andreprocessed by conventional thermoplastic processing techniques such asextrusion, injection molding, compression molding, etc. Scrap and orflashing can also be salvaged and reprocessed. In a typical dynamicvulcanization process, curative addition is altered so as tosubstantially simultaneously mix and vulcanize, or crosslink, at leastone of the vulcanizable components in a composition comprising at leastone vulcanizable rubber, elastomer or polymer and at least one polymeror resin not vulcanizable using the vulcanizing agent(s) for the atleast one vulcanizable component. (See, e.g., U.S. Pat. No. 6,079,465and the references cited therein.) However, in the present invention,the dynamic vulcanization process is further modified, as describedbelow, in order to achieve the particular advantages resulting from suchmodification.

The following are common curatives that can function in the presentinvention: ZnO, CaO, MgO, Al₂O₃, CrO₃, FeO, Fe₂O₃, and NiO. These metaloxides can be used in conjunction with the corresponding metal stearatecomplex (e.g., the stearate salts of Zn, Ca, Mg, and Al), or withstearic acid, and either a sulfur compound or an alkylperoxide compound.(See also, Formulation Design and Curing Characteristics of NBR Mixesfor Seals, RUBBER WORLD 25-30 (1993). To the curative agent(s) there areoften added accelerators for the vulcanization of elastomercompositions. The curing agent(s), with or without the use of at leastone accelerator, is often referred to in the art as a curing “system”for the elastomer(s). A cure system is used because typically more thanone curing agent is employed for beneficial effects, particularly wherea mixture of high diene rubber and a less reactive elastomer is used.Furthermore, because the present invention employs a specificallydefined DVA process, it is necessary that the properties of the curesystem are adapted to the mixing process so that the conditions of theinvention can be met. In particular, the present DVA process utilizesthe staged addition of the vulcanizable rubber component(s) wherein therubber(s) to be dynamically vulcanized are added in at least twoportions. Furthermore, it is necessary that all of the rubber added in astage be cured before the rubber(s) in the next stage are added, suchtime period being characterized or measured by the mixer residence time.Typically the first, or if there are more than two stages of rubberaddition, then in a preceding stage, rubber(s) are cured to a level ofabout 50% of the maximum cure which the particular rubber(s) and curesystem are capable of reaching at the temperature of cure if measuredindependently of the dynamic vulcanization process in a time period thatis less than about the mixer residence time. For example, in order todetermine the cure response of the particular rubber(s) present in acomposition, the rubber(s) and cure system can be combined by meansknown to those skilled in the art, e.g., on a two-roll mill, Banburymixer or mixing extruder. A sample of the mixture, often referred to asthe “accelerated” compound, can be cured under static conditions, suchas in the form of a thin sheet using a mold that is subjected to heatand pressure in a press. Samples of the accelerated compound, cured asthin pads for progressively longer times and/or at higher temperatures,are then tested for stress strain properties and/or crosslink density todetermine the state of cure (described in detail in American Society forTesting and Materials, Standard ASTM D412).

Alternatively, the accelerated compound can be tested for state of cureusing an oscillating disc cure rheometer test (described in detail inAmerican Society for Testing and Materials, Standard ASTM D2084). Havingestablished the maximum degree of cure, it is preferable to dynamicallyvulcanize the first or preceding stage rubber(s) added to thedynamically vulcanizable mixture to the extent that the degree of cureof such rubber(s) is selected from the group consisting of about 50%,for example, about 60% to greater than about 95%; about 65% to about95%; about 70% to about 95%; about 75% to greater than about 90%; about80% to about 98%; about 85% to about 95%; and about 85% to about 99% ina time period less than or substantially equivalent to about theresidence time of the mixer used for dynamic vulcanization. Subsequentadditions of rubber(s) to the dynamically vulcanizable mixture aresimilarly cured before further additions of rubber(s), if any.Consequently, at the conclusion of the dynamic vulcanization process,the vulcanizable rubbers added to the composition are sufficiently curedto achieve the desired properties of the thermoplastic composition ofwhich they are a part, e.g., a fluid (air or liquid) retention barriersuch as a innerliner for a tire. For purposes of the present invention,such state of cure can be referred to as “substantially fully cured.”

It will be appreciated that the vulcanizable rubbers will be cured to atleast 50% of the maximum state of cure of which they are capable basedon the cure system, time and temperature, and typically, the state ofcure of such rubbers will exceed 50% of maximum cure. If the cure stateof the rubber(s) added in one stage are not cured to at least about 50%of their maximum, it is possible for dispersed rubber particles tocoalesce into larger size particles, particularly during the mixingoperations, which is undesirable. Conversely, it may be desirable tocure the rubber particles to less than the maximum state of cure ofwhich the rubber is capable so that the flexibility, as measured, forexample, by Young's modulus, of the rubber component is at a suitablelevel for the end-use to which the composition is to be put, e.g., atire innerliner or hose component. Consequently, it may be desirable tocontrol the state of cure of the rubber(s) used in the composition to beless than or equal to about 95% of the maximum degree of cure of whichthey are capable, as described above.

For purposes of dynamic vulcanization in the presence of an engineeringresin to form, for example, a highly impermeable layer or film, anyconventional curative system which is capable of vulcanizing saturatedor unsaturated halogenated polymers may be used to vulcanize at leastthe elastomeric halogenated copolymer of a C₄ to C₇ isomonoolefin and apara-alkylstyrene, except that peroxide curatives are specificallyexcluded from the practice of this invention when there is present oneor more thermoplastic engineering resins such that peroxide would causesuch resins themselves to crosslink. In that circumstance, if theengineering resin would itself vulcanize or crosslink, it would resultin an excessively cured, non-thermoplastic composition. Suitablecurative systems for the elastomeric halogenated copolymer component ofthe present invention include zinc oxide in combination with zincstearate or stearic acid and, optionally, one or more of the followingaccelerators or vulcanizing agents: Permalux (thedi-ortho-tolylguanidine salt of dicatechol borate); HVA-2 (m-phenylenebis maleimide); Zisnet (2,4,6-trimercapto-5-triazine); ZDEDC (zincdiethyl dithiocarbamate) and also including for the purposes of thepresent invention, other dithiocarbamates; Tetrone A (dipentamethylenethiuram hexasulfide); Vultac 5 (alkylated phenol disulfide); SP1045(phenol formaldehyde resin); SP1056 (brominated alkyl phenolformaldehyde resin); DPPD (diphenyl phenylene diamine); salicylic acid,ortho-hydroxy benzoic acid; wood rosin, abietic acid; and TMTDS(tetramethyl thiuram disulfide), used in combination with sulfur.However, in the present invention, since each addition of vulcanizablerubber(s) must be cured to at least 50% of its, or their, maximum stateof cure under the temperature conditions of the process before the nextaddition of rubber(s), as measured by the residence time of the mixingdevice, it is also necessary to adjust the composition of the curesystem to achieve such a suitable result. The methods by which this canbe achieved are generally known to those skilled in this art and arefurther described in detail above, e.g., by use of the method set forthin ASTM D2084.

Curative accelerators include amines, guanidines, thioureas, thiazoles,thiurams, sulfenamides, sulfenimides, thiocarbamates, xanthates, and thelike. Acceleration of the cure process may be accomplished by adding tothe composition an amount of the accelerant. The mechanism foraccelerated vulcanization of rubber involves complex interactionsbetween the curative, accelerator, activators and polymers. Ideally allof the available curative is consumed in the formation of effectivecrosslinks which join individual polymer chains to one another andenhance the overall strength of the polymer matrix. Numerousaccelerators are known in the art and include, but are not limited to,the following: stearic acid, diphenyl guanidine (DPG),tetramethylthiuram disulfide (TMTD), 4,4′-dithiodimorpholine (DTDM),tetrabutylthiuram disulfide (TBTD), 2,2′-benzothiazyl disulfide (MBTS),hexamethylene-1,6-bisthiosulfate disodium salt dihydrate,2-(morpholinothio) benzothiazole (MBS or MOR), compositions of 90% MORand 10% MBTS (MOR 90), N-tertiarybutyl-2-benzothiazole sulfenamide(TBBS), and N-oxydiethylene thiocarbamyl-N-oxydiethylene sulfonamide(OTOS), zinc 2-ethyl hexanoate (ZEH), N,N′-diethyl thiourea. Curatives,accelerators and the cure systems of which they are a part that areuseful with one or more crosslinkable polymers are well-known in theart. The cure system can be dispersed in a suitable concentration intothe desired portion of the rubber component, the rubber componentoptionally containing one or more filler, extender and/or plasticizerby, e.g., mixing the rubber and the cure system components in a stepprior to addition of the rubber-containing composition to thethermoplastic using any mixing equipment commonly used in the rubberindustry for such purpose, e.g., a two-roll rubber mill, a Banburymixer, a mixing extruder and the like. Such mixing is commonly referredto as “accelerating” the rubber composition. Alternatively, the rubbercomposition can be accelerated in a stage of a mixing extruder prior tocarrying out dynamic vulcanization. It is particularly preferred thatthe cure system be dispersed in the rubber phase, or in a rubbercomposition also optionally including one or more fillers, extenders andother common ingredients for the intended end-use application, prior tothe addition of the rubber to the thermoplastic resin(s) in the mixingequipment in which it is intended to carry out dynamic vulcanization.

In one embodiment of the invention, at least one curing agent istypically present at about 0.1 to about 20 phr; alternatively at about0.5 to about 10 phr.

Useful combinations of curatives, cure modifiers and accelerators can beillustrated as follows: As a general rubber vulcanization agent, e.g., asulfur vulcanization agent, powdered sulfur, precipitated sulfur, highdispersion sulfur, surface-treated sulfur, insoluble sulfur,dimorpholinedisulfide, alkylphenoldisulfide, and mixtures thereof areuseful. Such compounds may be used in an amount of about 0.5 phr toabout 4 phr (parts by weight per 100 parts by weight of the elastomercomponent). Alternatively, where the use of such a material is feasiblein view of other polymer and resin components present an organicperoxide vulcanization agent, benzoylperoxide, t-butylhydroperoxide,2,4-dichlorobenzoylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethylhexane-2,5-di(peroxylbenzoate), and mixtures thereof. Whenused, such curatives can be present at a level of about 1 phr to about20 phr. Other useful curatives include phenol resin vulcanization agentssuch as a bromide of an alkylphenol resin or a mixed crosslinking agentsystem containing stannous chloride, chloroprene, or another halogendonor and an alkylphenol resin and mixtures thereof. Such agents can beused at a level of about 1 phr to about 20 phr. Alternatively, otheruseful curing agents, cure modifiers and useful levels include zincoxide and/or zinc stearate (about 0.05 phr to about 5 phr), stearic acid(about 0.1 phr to about 5 phr), magnesium oxide (about 0.5 phr to about4 phr), lyserge (10 to 20 phr or so), p-quinonedioxime,p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone,poly-p-dinitrosobenzene (about 0.5 phr to about 10 phr),methylenedianiline (about 0.05 phr to about 10 phr), and mixturesthereof. Further, if desired or necessary, one or more of avulcanization accelerator may be added in combination with thevulcanization agent, including for example, an aldehyde-ammonia,guanidine, thiazole, sulfenamide, thiuram, dithio acid salt, thiurea,and mixtures thereof, for example, in an amounts of about 0.1 phr toabout 5 phr or more.

The dynamic vulcanization process of the present invention isparticularly distinguished from those generally known in the prior artas a consequence of the use of staged addition of at least onevulcanizable rubber or elastomer component. Consequently, the processemploys several additions of at least one rubber component, preferablyat least two such additions although three, four or more can also beused. However, in each instance, the staging is subject to thevulcanization criteria, including mixer residence time, as describedabove. As described herein, the preferred polymer components comprisehalogenated isobutylene-containing copolymers as the vulcanizablecomponent(s), e.g., halogenated butyl such as chlorinated butyl orbrominated butyl, and brominated isobutylene-p-methylstyrene copolymer(BIMS copolymer), and a thermoplastic polymer such as nylon or a blendof various nylon polymers. It is particularly preferred that thedynamically vulcanized compositions of the present invention comprisethe rubber component(s) as a dispersed, substantially fully cured, phaseof small particle size in a continuous matrix of thermoplastic.

Without wishing to be bound by theory, it is believed that the finerubber dispersions thus obtained in the compositions of the presentinvention are the result, in part, of the chemical reaction between,e.g., benzylic bromine present in BIMS, or allylic halogen inhalogenated butyl, and terminal amines in polyamides at the phaseboundary between the dispersed rubber particles and the thermoplasticformed during mixing. The presence of such interfacial reactions duringblending and simultaneous reaction of two immiscible polymers avoidscoalescence of the small particle size dispersed rubber phase, therebyleading to particularly fine dispersions of the rubber phase. Theoccurrence of such interfacial reactions is commonly referred to as“reactive compatibilization” and is described, e.g., in U.S. Pat. Nos.5,571,864 and 6,469,087, incorporated herein by reference. At the sametime, because of the interfacial stability in these reactivecompatibilized immiscible systems, phase inversion of the higherconcentration, lower viscosity polymer blend component, the rubberphase, is inhibited as a consequence of the stabilizing effect ofinterfacial compatibilization.

Ordinarily, in a polymer blend based on two polymers of differentviscosity, polymer physics would dictate that the lower viscosity phasein such a blend is the continuous phase. (See, e.g., D. R. Paul and J.W. Barlow, J. Macromol. Sci., Rev. Macromol. Chem., C18 (1980), 109; V.I. Metelkin and V. S. Blekht, Kolloid. Zh., 46 (1984), 476, and L. A.Ultracki, J. Rheol., 35 (1991), 1615). The primary invention thateventually led to the introduction of commercial, dynamically vulcanizedalloys, or DVA was that by A. M. Gessler, U.S. Pat. No. 3,037,954.Subsequent compositions based on EPDM and polypropylene weresuccessfully developed and commercialized, (such as Santoprene®,Advanced Elastomer Systems), as a consequence of causing a higherconcentration, lower viscosity EPDM component to be the dispersed phaseby vulcanizing the EPDM during mixing of the polypropylene and EPDM in amixer. Even in the absence of reactive compatibilization, vulcanizationleads to the most significant increase in viscosity; in other words, theviscosity of a vulcanized component is effectively infinite and thethermoplastic phase can become the continuous phase. By imposing whatamounts to phase inversion, the maximum rubber content of EPDM rubber insuch systems can be increased to greater than 70 volume percent ofrubbers.

Furthermore, while again not wishing to be bound by theory, it isbelieved that according to packing theory, the maximum volume fractionof mono-dispersed spheres that can be put into a fixed volume, based ona hexagonal close packing arrangement is 0.74 or 74% of the availablevolume. The maximum volume fractions achievable based on random closepacking and cubic packing for mono-dispersed spheres are believed to be0.64 and 0.52, respectively. These computations are described in R. K.McGeary, J. Am. Ceram. Soc., 44 (1961), 513. In polymer blends, thedispersions are poly-dispersed which is beneficial in maximizing thepacked volume fraction. Taking these factors into consideration, it isexpected that maximum packing volume of a poly-dispersed polymer in abinary polymer blend would be about 70 to about 80 volume percent.However, because interfacial stabilization prevents phase inversion, themaximum rubber content in the dynamically vulcanized polyamide/BIMSsystems disclosed in EP 0 857 761 A1 and EP 0 969 039 A1 was limited toless than 60 volume %.

Higher rubber content can be achieved in the dynamically vulcanizedcompositions of the present invention as a consequence of furtherpacking of rubber particles through multi-stage mixing, provided thatthe previously occluded rubbers are substantially fully stable andcannot coalesce into larger sized domains. This can be achieved bycausing all rubber(s) incorporated in a given stage of mixing to besufficiently cured, in other words, reaching at least about 50% ofmaximum cure, (preferably at least about 60%, preferably at least about70%, preferably at least about 80%) before the next quantity of rubberis added, also referred to as the next stage of rubber addition. Thepreferred halogenated isobutylene elastomer content, typically presentin the composition in the form of particles, is greater than about 60volume %, most preferably greater than about 70 volume %. For example,the elastomer particles are present in an amount selected from the groupconsisting of greater than about 60 volume % to about 80 volume % (basedupon the volume of the elastomer(s) and the engineering resin(s)); about62 volume % to about 78 volume %; about 65 volume % to about 75 volume%; about 68 volume % to about 75 volume %; about 70 volume % to about 78volume %; about 71 volume % to about 80 volume %; about 72 volume % toabout 79 volume %; and about 71 volume % to about 80 volume %; forexample wherein said elastomer particles comprise about 62 volume % toabout 76 volume %. In the present invention, a thermoplastic elastomercomposition having high rubber content is achieved by use of multistageaddition of rubber(s) in which the cure rates of such rubbers arecontrolled to be less the mixer residence time, thereby achieving asufficiently high state of cure. Dynamic vulcanization can be carriedout in various types of commercial equipment generally available in therubber and plastics industry including Banbury internal mixers, rollmixers, and mixing extruders. The preferred mixing equipment is atwin-screw extruder with intermeshing screw. As described above, mixingis generally conducted under such time and temperature conditions thatthe dispersed rubber particles are cured to the extent necessary tomaintain their stability, i.e., to avoid coalescence of such particlesprior to or during the addition of the next stage of rubber addition orcompletion of mixing of the composition. A suitable range of dynamicvulcanization temperatures is typically from about the meltingtemperature of the resin(s) to about 300° C.; for example, thetemperature may range from about the melting temperature of the matrixresin(s) to about 275° C. Preferably dynamic vulcanization is carriedout at a temperature range from about 10° C. to about 50° C. above themelting temperature of the matrix resin. More preferably the mixingtemperature is about 20° C. to about 40° C. above the meltingtemperature of the polyamide or mixed polyamide thermoplastic matrix.

In one embodiment of the present invention the necessary amount ofcrosslinking agent(s) or cure system is dispersed in the elastomercomponent by mixing the crosslinking agent capable of crosslinking theelastomer into the elastomer component at a low to moderate temperature,insufficient to substantially activate the cure system, prior tocontacting the thus compounded elastomer component with the resincomponent(s) for the purpose of carrying out dynamic vulcanization ofthe mixture. Furthermore, when the elastomer is added to the resin instages or portions until the overall desired composition is achieved,each portion of the rubber composition can be the same, or, if desired,the amount of the cure system present in a portion of the rubber can bemodified to achieve a desired effect, e.g., greater or lesser degree ofcrosslinking of a portion of the elastomer. By this method thecrosslinking agent does not substantially react with the rubber, nordoes it have an opportunity to partially react with the thermoplasticresin to cause either molecular weight degradation or crosslinking ofthe resin. Furthermore, control of the crosslinking rate and extent ofcrosslinking of the elastomer component is more readily achieved.Consequently, the compositions of the present invention exhibit improvedproperties.

One process for producing of the thermoplastic elastomer composition canbe performed by the following procedure. First, a mixing device such asa Banbury mixer, two-roll rubber mill, etc. is used to pre-mix theelastomer component and predetermined amount of crosslinking agent untila substantially uniform dispersion is obtained. At this time, theelastomer component may have added thereto suitable amounts of optionalfillers such as carbon black or modified carbon black, clay or modifiedclay oil and/or plasticizer. During this phase of mixing the temperaturehas to be controlled at a low enough level for the particularelastomer(s) selected and in consideration of the activity of the curesystem, to avoid premature crosslinking of the elastomers. A usefultemperature during this mixing step can be less than about 120° C.

The desired amount of the crosslinking agent-containing elastomercomponent thus prepared and the predetermined amount of nylon resin(s)are preferably charged into a twin-screw mixing extruder or other mixingdevice capable of effecting dynamic vulcanization under controlledconditions. The rubber component is made to dynamically crosslink, whileeffecting the melt mixing of the resin(s) to cause the elastomercomponent to disperse as a dispersed phase (domain) in the nylon resinwhich forms the continuous phase or matrix.

Further, various compounding agents other than vulcanization agents maybe added to the nylon resin or elastomer component during the abovemixing, but it is preferable to mix them in advance before the dynamicvulcanization step. The mixing device used for the carrying out dynamicvulcanization of the nylon resin and elastomer component is notparticularly limited, including for example, a screw extruder, kneader,Banbury mixer, twin-screw mixing extruder, and the like. Among these, atwin-screw mixing extruder is preferably used for dynamic vulcanization.Alternatively, two or more types of mixers may be used in successivemixing operations. As the conditions for the dynamic vulcanization stepinvolving melt mixing of the resin(s), the temperature should be atleast the temperature at which the predetermined nylon resin melts, butpreferably above the melting temperature as described above.Furthermore, the shear rate at the time of mixing is typically greaterthan about 500 sec⁻¹; preferably about 500 to about 7500 sec⁻¹;alternatively, about 1000 to about 7500 sec⁻¹; for example about 2000 toabout 7500 sec⁻¹. The overall time of mixing during each stage ofdynamic vulcanization is preferably about 30 seconds to about 10minutes.

Since the process of the present invention involves multistage additionof the rubber component to the resin(s) or resin(s) plus previouslydynamically vulcanized and dispersed elastomer, the above dynamicvulcanization step is repeated with at least one or more additionalportions of the rubber composition until the total amount of rubberdesired in the final thermoplastic composition is achieved.Consequently, this process will involve a minimum of two stages, but canbe conducted in more than two such stages, e.g., three, four, five ormore, as desired. Furthermore, the amount of rubber introduced in eachstage can be varied, provided the total amount of rubber desired in theoverall composition is achieved at the conclusion of all of the mixingoperations and a suitable amount of rubber is introduced in each stageso as to achieve the desired small particle size and high volume percentof rubber in the final composition.

The thermoplastic elastomer composition thus obtained is structured withthe elastomer component forming a discontinuous phase dispersed as adispersion phase (domain) in a matrix of the nylon resin which forms acontinuous phase. As a consequence of dynamic vulcanization, thecomposition remains thermoplastic and a film, layer or sheet-likestructure of the composition can be formed using ordinary molding,extrusion or calendering. This result is illustrated in FIG. 1 which isa view of the microstructure shown by an atomic force microscope tappingphase micrograph (20 by 20 micron area) of the thermoplastic elastomercomposition obtained according to the embodiment of Example 13 describedbelow. The figure shows a high concentration of small particulate orglobular areas of vulcanized brominated isobutylene paramethyl styreneelastomer dispersed in a continuous polyamide matrix, the continuousmatrix having the appearance of a lighter region surrounding thediscrete elastomer particles.

The composition described herein may also have one or more fillercomponents such as calcium carbonate, clay, mica, silica and silicates,talc, titanium dioxide, starch and other organic fillers such as woodflour, and carbon black. Suitable filler materials include carbon blacksuch as channel black, furnace black, thermal black, acetylene black,lamp black, modified carbon black such as silica treated or silicacoated carbon black (described, for example, in U.S. Pat. No. 5,916,934,incorporated herein by reference), and the like. Reinforcing gradecarbon black is preferred. The filler may also include other reinforcingor non-reinforcing materials such as silica, clay, calcium carbonate,talc, titanium dioxide and the like. The filler may be present at alevel of from 0 to about 30 percent by weight of the rubber present inthe composition.

Exfoliated, intercalated, or dispersed clays may also be present in thecomposition. These clays, also referred to as “nanoclays”, are wellknown, and their identity, methods of preparation and blending withpolymers is disclosed in, for example, JP 2000109635, JP 2000109605, JP11310643; DE 19726278; WO98/53000; and U.S. Pat. Nos. 5,091,462,4,431,755, 4,472,538, and 5,910,523. Swellable layered clay materialssuitable for the purposes of the present invention include natural orsynthetic phyllosilicates, particularly smectic clays such asmontmorillonite, nontronite, beidellite, volkonskoite, laponite,hectorite, saponite, sauconite, magadite, kenyaite, stevensite and thelike, as well as vermiculite, halloysite, aluminate oxides, hydrotalciteand the like. These layered clays generally comprise particlescontaining a plurality of silicate platelets having a thicknesstypically about 4 to about 20 Å in one embodiment, and about 8 to about12 Å in another embodiment, bound together and containing exchangeablecations such as Na⁺, Ca⁺², K⁺ or Mg⁺² present at the interlayersurfaces.

Layered clay may be intercalated and exfoliated by treatment withorganic molecules (swelling agents) capable of undergoing ion exchangereactions with the cations present at the interlayer surfaces of thelayered silicate. Suitable swelling agents include cationic surfactantssuch as ammonium, alkylamines or alkylammonium (primary, secondary,tertiary and quaternary), phosphonium or sulfonium derivatives ofaliphatic, aromatic or arylaliphatic amines, phosphines and sulfides.Desirable amine compounds (or the corresponding ammonium ion) are thosewith the structure R₁R₂R₃N, wherein R₁, R₂, and R₃ are C₁ to C₃₀ alkylsor alkenes which may be the same or different. In one embodiment, theexfoliating agent is a so-called long chain tertiary amine, wherein atleast R₁ is a C₁₂ to C₂₀ alkyl or alkene.

Another class of swelling agents include those which can be covalentlybonded to the interlayer surfaces. These include polysilanes of thestructure —Si(R′)₂R² where R′ is the same or different at eachoccurrence and is selected from alkyl, alkoxy or oxysilane and R² is anorganic radical compatible with the matrix polymer of the composite.Other suitable swelling agents include protonated amino acids and saltsthereof containing 2-30 carbon atoms such as 12-aminododecanoic acid,epsilon-caprolactam and like materials. Suitable swelling agents andprocesses for intercalating layered silicates are disclosed in U.S. Pat.Nos. 4,472,538, 4,810,734, 4,889,885 and WO92/02582.

In a preferred embodiment of the invention, the exfoliating or swellingagent is combined with a halogenated polymer. In one embodiment, theagent includes all primary, secondary and tertiary amines andphosphines; alkyl and aryl sulfides and thiols; and their polyfunctionalversions. Desirable additives include: long-chain tertiary amines suchas N,N-dimethyl-octadecylamine, N,N-dioctadecyl-methylamine,dihydrogenated tallowalkyl-methylamine and the like, andamine-terminated polytetrahydrofuran; long-chain thiol and thiosulfatecompounds such as hexamethylene sodium thiosulfate. In anotherembodiment of the invention, improved interpolymer impermeability isachieved by the use of polyfunctional curatives such as hexamethylenebis(sodium thiosulfate) and hexamethylene bis(cinnamaldehyde).

The amount of exfoliated, intercalated, or dispersed clay incorporatedin the composition in accordance with this invention is an amountsufficient to develop an improvement in the mechanical properties orbarrier properties of the composition, e.g. tensile strength orair/oxygen permeability. Amounts typically can be from about 0.5 toabout 15 wt % in one embodiment, or about 1 to about 10 wt % in anotherembodiment, and about 1 to about 5 wt % in yet another embodiment, basedon the polymer content of the composition. Expressed in parts perhundred rubber, the exfoliated, intercalated, or dispersed clay may bepresent at about 1 to about 30 phr in one embodiment, and about 3 toabout 20 phr in another embodiment. In one embodiment, the exfoliatingclay is an alkylamine-exfoliating clay.

As used herein, the term “process oil” means both the petroleum derivedprocess oils and synthetic plasticizers. A process or plasticizer oilmay be present in air barrier compositions. Such oils are primarily usedto improve the processing of the composition during preparation of thelayer, e.g., mixing, calendering, etc. Suitable plasticizer oils includealiphatic acid esters or hydrocarbon plasticizer oils such as paraffinicor naphthenic petroleum oils. The preferred plasticizer oil for use instandard, non-DVA, non-engineering resin-containing innerlinercompositions is a paraffinic petroleum oil; suitable hydrocarbonplasticizer oils for use in such innerliners include oils having thefollowing general characteristics.

Property Preferred Minimum Maximum API gravity at 15-30 10 35 60° F.(15.5° C.) Flash Point, 330-450 300 700 (open cup (165-232° C.) (148°C.) (371° C.) method) ° F. (° C.) Pour Point, ° F. 30 to +30 −35  60 (°C.) (−34 to −1° C.) (−37° C.)  (15° C.)Generally, the process oil may be selected from paraffinic oils,aromatic oils, naphthenic oils, and polybutene oils. Polybutene processoil is a low molecular weight (less than 15,000 Mn) homopolymer orcopolymer of olefin-derived units having from about 3 to about 8 carbonatoms, more preferably about 4 to about 6 carbon atoms. In anotherembodiment, the polybutene oil is a homopolymer or copolymer of a C₄raffinate. Low molecular weight “polybutene” polymers is described in,for example, SYNTHETIC LUBRICANTS AND HIGH-PERFORMANCE FUNCTIONAL FLUIDS357-392 (Leslie R. Rudnick & Ronald L. Shubkin, ed., Marcel Dekker 1999)(hereinafter “polybutene processing oil” or “polybutene”). Usefulexamples of polybutene oils are the PARAPOL™ series of processing oils(previously available form ExxonMobil Chemical Company, Houston Tex.,now available from Infineum International Limited, Milton Hill, Englandunder the “INFINEUM c, d, f or g tradename), including grades previouslyidentified as PARAPOL™ 450, 700, 950, 1300, 2400, and 2500. Additionallypreferred polybutene oils are SUNTEX™ polybutene oils available from SunChemicals. Preferred polybutene processing oils are typically syntheticliquid polybutenes having a certain molecular weight, preferably fromabout 420 Mn to about 2700 Mn. The molecular weight distribution -Mw/Mn-(“MWD”) of preferred polybutene oils is typically about from 1.8 toabout 3, preferably about 2 to about 2.8. The preferred density (g/ml)of useful polybutene processing oils varies from about 0.85 to about0.91. The bromine number (CG/G) for preferred polybutene oils rangesfrom about 40 for the 450 Mn process oil, to about 8 for the 2700 Mnprocess oil.

Rubber process oils also have ASTM designations depending on whetherthey fall into the class of paraffinic, naphthenic or aromatichydrocarbonaceous process oils. The type of process oil utilized will bethat customarily used in conjunction with a type of elastomer componentand a rubber chemist of ordinary skill in the art will recognize whichtype of oil should be utilized with a particular rubber in a particularapplication. For an innerliner composition the oil is typically presentat a level of 0 to about 25 wt %; preferably about 5 to 20 wt % of thetotal composition. For a thermoplastic elastomer composition the oil maybe present at a level of 0 to about 20 wt % of the total composition;preferably oil is not included in order to maximize impermeability ofthe composition.

In addition, plasticizers such as organic esters and other syntheticplasticizers can be used. A particularly preferred plasticizer for usein a DVA composition is N-butylsulfonamide or other plasticizerssuitable for polyamides. In another embodiment, rubber process oils suchas naphthenic, aromatic or paraffinic extender oils may be present atabout 1 to about 5 phr. In still another embodiment, naphthenic,aliphatic, paraffinic and other aromatic oils are substantially absentfrom the composition. By “substantially absent”, it is meant thatnaphthenic, aliphatic, paraffinic and other aromatic oils may bepresent, if at all, to an extent no greater than 2 phr in thecomposition.

The degree of cure of the vulcanized rubber can be described in terms ofgel content, cross-link density, the amount of extractable components orit can be based on the state of cure that would be achieved in therubber were it to be cured in the absence of the resin. For example, inthe present invention, it is preferred that the halogenated elastomerachieve about 50 to about 85% of full cure based on the elastomer per seas measured, e.g., by tensile strength or using the oscillating disccure meter test (ASTM D 2084, Standard Test Method for RubberProperty-Vulcanization Using Oscillating Disk Cure Meter).

By molding the thermoplastic elastomer composition obtained into asheet, film, or tube using a T-sheeting die, straight or crossheadstructure tubing die, inflation molding cylindrical die, etc. at the endof a single-screw extruder, or by calendering, it is possible to use thecomposition as the air permeation preventive layer, e.g., an innerliner,of a pneumatic tire and as a component or layer of a hose, etc. Thethermoplastic elastomer compositions of the present invention may betaken up into strands once, pelletized, then molded by using asingle-screw extruder that is typically used for resin.

The sheet or tubular molded article thus obtained can be effectivelyused for an innerliner layer of a pneumatic tire or the hose tube orhose cover of a low gas permeable hose. Furthermore, the lowpermeability characteristics of the composition are suitable for useswith fluids other than gasses, e.g., liquids such as water, hydraulicfluid, brake fluid, heat transfer fluid, etc., provided that the layerin direct contact with the fluid has suitable resistance to the fluidbeing handled.

Any range of numbers recited in the specification hereinabove or in theparagraphs and claims hereinafter, referring to various aspects of theinvention, such as that representing a particular set of properties,units of measure, conditions, physical states or percentages, isintended to literally incorporate expressly herein by reference orotherwise, any number falling within such range, including any subset ofnumbers or ranges subsumed within any range so recited. Furthermore, theterm “about” when used as a modifier for, or in conjunction with, avariable, characteristic or condition is intended to convey that thenumbers, ranges, characteristics and conditions disclosed herein areflexible and that practice of the present invention by those skilled inthe art using temperatures, times, concentrations, amounts, contents,carbon numbers, properties such as particle size, surface area, bulkdensity, etc., that are outside of the range or different from a singlevalue, will achieve the desired result, namely, an dynamicallyvulcanized, high elastomer-content composition comprising at least oneisobutylene-containing elastomer and at least one thermoplastic suitablefor use, for example, in a pneumatic tire or hose, or as a tireinnerliner.

EXAMPLES

The following commercially available products were used for thecomponents employed in the Examples

Description Rubber Components BIIR Bromobutyl ™ 2222 (brominatedisobutylene isoprene copolymer, 2% Br, ExxonMobil Chemical Company,Houston Texas) BIMS-2 Exxpro ™ 96-1 (brominated isobutylene p-methylstyrene copolymer, 0.5% Br, 5% PMS, ExxonMobil Chemical Company HoustonTexas) BIMS-1 Exxpro ™ 89-4 (brominated isobutylene p-methyl styrenecopolymer, 0.75% Br, 5% PMS, ExxonMobil Chemical) NR SMR-20 naturalrubber (Standard Malaysian Rubber) SBR Copo ™-1502 (styrene-butadienerubber, 23.5% bound styrene, DSM Copolymer, Netherlands) Cure SystemComponents ZnO Zinc oxide - cure system component St-acid Stearic acid -cure system component ZnSt Zinc state - cure system component S sulfur -cure system component MBTS sulfur-containing cure systemaccelerator2,2′-benzothiazyl disulfide C1 Cure modifier1, 6PPD, N-(1,3-dimethylbutyl)-N′-phenyl-p- phenylenediamine C2 Cure modifier 2, ArmeenDMHR, dimethyl hydrogenated rapeseed (C₂₀-C₂₂) tertiary amine, AkzoNobel Additive Components Struktol Compound compatibilizer (mixture of40MS dark aromatic hydrocarbon resins, Struktol Company) Calsol 810naphthenic processing oil (Calumet Lubricants) Flectol Flectol TMQantioxidant (polymerized 1,2-dihydro-2,2,4- trimethylquinoline, FlexsysAmerica) N660 Carbon black (semi-reinforcing grade) N39S2 Silica coatedcarbon black T1 SP1068 (tackifier 1 - alkyl phenol formaldehyde resin,Schenectady International) T2 G100 (tackifier 2 - synthetic polyterpeneresin (Quintone brand, Nippon Zeon Chemicals) T3 Sylvalite RE100L(tackifier 3 - pentaerythritol ester of rosin, Arizona Chemical)Engineering Resin Component N11 Nylon 11 available as Rilsan BMN O fromArkema N6/66-1 Nylon 6/66 copolymer available as Ube 5033B from UbeN6/66-2 Nylon 6/66 copolymer available as Ube 5034B from Ube N6/66-3Nylon 6/66 copolymer available as CM6001FS available from Toray AdditiveComponent P Plasticizer, BM4, N- butylsulfonamide C Compatibilizer,AR201, maleated EVA copolymer DuPont-Mitsui S1 Stabilizer 1, packageincludes Irganox, Tinuvin, and Copper Iodide (CuI) S2 Stabilizer 2,package includes Irgafos 168; (tris(2,4-di-(tert)-butylphenyl)phosphite) (Ciba Specialty Chemicals)In accordance to formulations listed in Table 1, where compositions areexpressed as parts per hundred of rubber or phr (unless otherwisenoted), examples 1 to 4 were prepared using a dynamic vulcanizationprocess carried out in a twin-screw extruder at 230° C. Specifically,the DVA's were prepared according to the procedure described in EP 0 969039, with specific reference to the section entitled “Production ofThermoplastic Elastomer Composition.” The elastomer component andvulcanization system were charged into a kneader, mixed forapproximately 3.5 minutes, and dumped out at about 90° C. to prepare anelastomer component with a vulcanization system. The mixture was thenpelletized by a rubber pelletizer. Next, the elastomer component andresin components were charged into a twin screw mixing extruder anddynamically vulcanized to prepare a thermoplastic elastomer composition.BIMS content was steadily increased until phase inversion was observed,i.e., until the BIMS phase became continuous. BIMS content was increasedin Table 1 from Example 1 to Example 4 by raising the elastomercomponent feed to the extruder according to the formulations specifiedin Table 1. As shown in Table 1, poor dispersion resulted at 62.5%rubber content and phase inversion, when the BIMS rubber phase becamecontinuous, occurred at 70% rubber content. Good extrudate quality,typically characterized by a smooth surface and constant stranddiameter, was obtained only for the compositions of examples 1 and 2, asshown in Table 1.

TABLE 1 Example 1 2 3 4 BIMS-2 100 100 100 100 ZnO 0.15 0.15 0.15 0.15St-acid 0.60 0.60 0.60 0.60 ZnSt 0.30 0.30 0.30 0.30 N11 44.6 40.2 36.228.4 N6/66-1 30.7 27.7 24.9 19.5 P 10.5 9.5 8.6 6.7 S 0.87 0.79 0.710.56 BIMS vol % 57.5 60 62.5 70 Quality Good Good Poor Phase invertedM50 (MPa) 6.4 5.9 5.8 NM Elongation 370 340 320 NM (%) Fatigue 1.5 M 2.5M 2.3 M NM (cycles) M50: 50% modulus at room temperature measuredaccording to ASTM D412-92; Elongation: elongation to break at roomtemperature measured according to ASTM D412-92; Fatigue: samples testedat 40% strain amplitude in tensile mode running at 6.67 Hz and at roomtemperature; fatigue resistance expressed in cycles to failure. M meansmillion. NM means cannot be measuredAccording to the phase continuity criterion, raising the BIMS rubberviscosity could further extend the rubber content. In examples 5-9, 20phr of silica coated carbon black filler was added to the rubbercomposition to increase the viscosity of the rubber composition. Theelastomer components, BIMS rubber and its viscosity modifier of silicacoated carbon black, were mixed in a Banbury mixer for 3 to 5 minutesand dumped at 120° C. Subsequently, the rubber-carbon black mixes wereaccelerated with the curatives in a kneader and dumped at about 90° C.These elastomer mixtures were then pelletized by a rubber pelletizer andused as the elastomer component feeds for the twin screw extrusionmixing with nylons. All nylon and elastomer components were metered to atwin screw extrusion mixer running at 230° C. and at 100 rpm. As shownin Table 2, phase inversion still occurred at 70 volume % of rubberalthough good quality mixing can be obtained with rubber content up to62.5 volume %. However, fatigue resistance of the carbon black fillercontaining, dynamic vulcanized polyamide/BIMS blends is compromised inthese compositions.

TABLE 2 Example 5 6 7 8 9 BIMS-2 100 100 100 100 100 N39S2 20 20 20 2020 ZnO 0.15 0.15 0.15 0.15 0.15 St-acid 0.60 0.60 0.60 0.60 0.60 ZnSt0.30 0.30 0.30 0.30 0.30 N11 49.1 44.3 39.9 35.8 28.7 N6/66-1 33.8 30.527.4 24.6 19.7 P 11.6 10.5 9.4 8.5 6.8 S1 0.96 0.87 0.78 0.69 0.56 BIMSvol % 57.5 60 62.5 65 70 Quality Good Good Good Poor Phase inverted M50(MPa) 7.8 7.0 6.3 5.6 NM Elongation 300 340 360 370 NM (%) Fatigue 1.0 M0.6 M 0.7 M 0.7 M NM M50: 50% modulus at room temperature measuredaccording to ASTM D412-92; Elongation: elongation to break at roomtemperature measured according to ASTM D412-92; Fatigue: samples testedat 40% strain amplitude in tensile mode running at 6.67 Hz and at roomtemperature; fatigue resistance expressed in cycles to failure. M meansmillion. NM means cannot be measuredExamples 10 to 14 were prepared using a ZSK-30 co-rotating intermeshingtwin screw extruder with 29 length to diameter (L/D) screw and aresidence time of about 1 minute at 100 RPM. As indicated in Table 3,example 10 with long cure time, greater than 60 minutes, encounteredphase inversion during the first mix. C1 and C2 are the two curemodifiers in combination with S2 stabilizer and were adjusted to providedifferent cure times. Curatives were pre-dispersed in BIMS rubber usinga Banbury internal mixer running at 60 RPM with a dump temperature of100° C. Curatives-containing BIMS rubber composition was then pelletizedusing a granulator prior to being fed to the mixing extruder. The curetime of example 11 is slightly higher than the residence time of theextruder and, in turn, led to phase inversion during the second mixing.When the cure time is less than 1 minute, as that of examples 12-14,acceptable extrusion quality with high rubber contents could be obtainedin two-stage mixing.

As shown in Tables 1 and 2, the maximum rubber content achievable by theone-stage mixing, even with the increase in rubber viscosity, is 62.5%.Table 3 deals with two stage mixing.

TABLE 3 Example 10 11 12 13 14 BIMS-1 100 100 100 100 100 ZnO 0 1.0 0.50.5 0.5 St. acid 0 1.5 0.5 0.5 0.5 C1 1 0 1 1 1 C2 0.5 0.5 0.5 0 0N6/66-2 120 0 0 0 0 N6/66-3 0 78 78 78 49 S2 0.6 0.4 0.4 0.4 0.25 Curetime >60 1.09 0.79 0.70 0.70 First Mix** 55/45 55/45 55/45 55/45 55/45Rubber particle NM 0.18 0.29 0.20 0.20 size Second Mix** NM 80/20 80/2080/20 70/30 Final rubber vol — 62 62 62 73 % Rubber particle NM NM 0.170.22 0.24 size Observation Phase inverted Phase Good Good Good invertedM50 (MPa) NM NM 16 21 8.5 Cure Time is cure time in minutes measuredbased on time required to reach 50% cure at 230° C. using MDR curemeter(ASTM D2084-92A); Rubber particle size: number average rubber dispersiondiameter in microns measured by tapping phase atomic force microscopeand image processing; NM: cannot be measured, since phase inversion wasencountered; M50: 50% modulus at room temperature imeasured according toASTM D412-92 First Mix** 55/45 means addition of 55 wt. % Nylon and 45wt. % (approximately 50 vol. %) rubber. Second Mix** 80/20 meansaddition of 80 parts by weight of the first mix composition plus 20parts by weight of rubber. Second Mix** 70/30 means addition of 70 partsby weight of the first mix composition plus 30 parts by weight ofrubber.Melt viscosity properties of components and mixtures were also measuredwith the following results (melt viscosity at 230° C. and 1216 sec⁻¹shear rate measured using a Monsanto processability tester):

TABLE 4 Component or mixture Viscosity (Pa-s) Exxpro 89-4 250 N6/66-1600 N6/66-2 600 N6/66-3 150 N11 200 First Mix 200Thus, the viscosity ratio of the resin to the rubber during the firstmix is 0.6 and the viscosity ratio of the first mix to the rubber duringthe second mix is 0.8. Furthermore, since the viscosity of a mixture ofthe rubber plus cure system in the absence of crosslinking would besubstantially the same as that of the rubber, a similar ratio would beobtained.

All documents described herein are incorporated by reference herein,including any priority documents and/or testing procedures to the extentthey are not inconsistent with this text. The principles, preferredembodiments, and modes of operation of the present invention have beendescribed in the foregoing specification. Although the invention hereinhas been described with reference to particular embodiments, it is to beunderstood that these embodiments are merely illustrative of theprinciples and applications of the present invention. It is therefore tobe understood that numerous modifications may be made to theillustrative embodiments and that other arrangements may be devisedwithout departing from the spirit and scope of the present invention asdefined by the appended claims. Likewise, the term “comprising” isconsidered synonymous with the term “including” for purposes ofAustralian law.

Various aspects or embodiments of the present invention are set forth inthe following enumerated paragraphs: This invention relates to:

1. A thermoplastic elastomer composition comprising

-   -   (A) at least one halogenated isobutylene-containing elastomer;        and    -   (B) at least one nylon resin having a melting point of about        170° C. to about 230° C.; wherein:    -   (1) said at least one elastomer is present as a dispersed phase        of small vulcanized particles in a continuous phase of said        nylon;    -   (2) said elastomer particles have been formed by dynamic        vulcanization; and    -   (3) said elastomer particles comprising greater than about 60        volume % of the volume of said elastomer and said resin.        2. The composition according to paragraph 1 wherein said        elastomer particles are present in an amount selected from the        group consisting of greater than about 60 volume % to about 80        volume %; about 62 volume % to about 78 volume %; about 65        volume % to about 75 volume %; about 68 volume % to about 75        volume %; about 70 volume % to about 78 volume %; about 71        volume % to about 80 volume %; and about 72 volume % to about 79        volume %.        3. The composition according to paragraph 1 wherein said        elastomer particles comprise greater than about 65 volume %.        4. The composition according to paragraph 1 wherein said        elastomer particles comprise greater than about 62 volume %.        5. The composition according to paragraph 1 wherein said        elastomer particles comprise about 62 volume % to about 78        volume %.        6. The composition according to paragraph 1 wherein said        elastomer particles comprise about 62 volume % to about 76        volume %.        7. The composition according to paragraph 1 wherein the degree        of cure of said elastomer particles is at least about 50% of the        maximum degree of cure that said elastomer is capable of        reaching based on the composition and conditions under which        said elastomer is vulcanized.        8. The composition according to paragraph 7 wherein said degree        of cure is selected from the group consisting of about 60% to        greater than about 95%; about 65% to about 95%; about 70% to        about 95%; about 75% to greater than about 90%; about 80% to        about 98%; about 85% to about 95%; and about 85% to about 99%.        9. The composition according to paragraph 7 wherein said degree        of cure is at least about 80%.        10. The composition according to paragraph 1 further comprising        at least one component selected from the group consisting of        fillers and plasticizers.        11. The composition according to paragraph 1 wherein said nylon        resin comprises a mixture of (i) nylon 11 or nylon 12; and (ii)        nylon 6/66 copolymer, and a composition ratio of (i)/(ii) is        about 10/90 to about 90/10.        12. The composition according to paragraph 11 wherein said        composition ratio of (i)/(ii) is about 30/70 to about 85/15.        13. The composition according to paragraph 1 wherein said at        least one halogenated isobutylene-containing elastomer is        selected from the group consisting of halogenated butyl rubber,        halogenated isoolefin/para-alkylstyrene copolymer, halogenated        isobutylene-p-methylstyrene-isoprene copolymer, halogenated        branched butyl rubber and halogenated star-branched butyl        rubber.        14. The composition according to paragraph 13 wherein said        halogenated butyl rubber halogenated butyl rubber comprises a        high content of the following halogenated structure, where X        represents a halogen:

15. The composition according to paragraph 13 or paragraph 14 whereinthe halogen is selected from the group consisting of bromine andchlorine.16. The composition according to paragraph 13 wherein said halogenatedisoolefin/para-alkylstyrene copolymer copolymers comprises a C₄ to C₇isoolefin.17. The composition according to paragraph 16 wherein said halogenatedisoolefin/para-alkylstyrene copolymer comprises a halogenatedpoly(isobutylene-co-p-methylstyrene) copolymer.18. The composition according to paragraph 17 wherein said halogen isbromine.19. A pneumatic tire comprising an air permeation preventive layercomprising a thermoplastic elastomer composition according to paragraph1.20. A hose comprising a thermoplastic elastomer composition according toparagraph 1 as at least one layer of a hose tube material.21. A process conducted in a suitable mixer for producing athermoplastic elastomer composition, said mixer having a characteristicresidence time, said composition comprising greater than about 60 volume% of dispersed particles of a total amount of at least one halogenatedisobutylene-containing elastomer, said particles dispersed in acontinuous thermoplastic nylon resin matrix, said process comprising thesteps of:

-   -   (1) mixing halogenated elastomer-containing composition (A),        said composition (A) comprising a first fraction of the total        amount of halogenated elastomer in said thermoplastic elastomer        composition and further comprising a cure system for said first        elastomer fraction; and thermoplastic nylon resin (B) under        suitable dynamic vulcanization conditions of time, temperature        and shear to form composition (C);    -   (2) mixing composition (C) and halogenated elastomer-containing        composition (D), said composition (D) comprising a second        fraction of the total amount of halogenated elastomer in said        thermoplastic elastomer composition and further comprising a        cure system for said second elastomer fraction; under suitable        dynamic vulcanization conditions of time, temperature and shear        to form composition (E);    -   (3) if the sum of said first and second fractions of halogenated        elastomer is less than the total amount of halogenated elastomer        in said thermoplastic elastomer composition, mixing        composition (E) and halogenated elastomer-containing composition        (F), said composition (F) comprising a third fraction of the        total amount of halogenated elastomer in said thermoplastic        elastomer composition and further comprising a cure system for        said third elastomer fraction; under suitable dynamic        vulcanization conditions of time, temperature and shear to form        composition (G); wherein the step of dynamically vulcanizing a        fractional additional amount of halogenated elastomer in the        presence of the dynamically vulcanized composition of the        preceding step is repeated as many times as necessary in order        to obtain the total amount of halogenated elastomer in said        thermoplastic elastomer composition; and wherein each said        dynamic vulcanization conditions at each step are sufficient to        effect a cure state in said elastomer particles of at least        about 50% of the maximum cure state for said elastomer and cure        system and wherein said dynamic vulcanization time period is        equal to or less than about the characteristic residence time of        said mixer.        22. The process according to paragraph 21 comprising two        fractional additions of said halogenated elastomer.        23. The process according to paragraph 21 comprising at least        three fractional additions of said halogenated elastomer.        24. The process according to paragraph 21 wherein said elastomer        particles are present in an amount selected from the group        consisting of greater than about 60 volume % to about 80 volume        %; about 62 volume % to about 78 volume %; about 65 volume % to        about 75 volume %; about 68 volume % to about 75 volume %; about        70 volume % to about 78 volume %; about 71 volume % to about 80        volume %; about 72 volume % to about 79 volume %; and about 71        volume % to about 80 volume %.        25. The process according to paragraph 21 wherein said elastomer        particles comprise greater than about 65 volume %.        26. The process according to paragraph 21 wherein said elastomer        particles comprise greater than about 62 volume %.        27. The process according to paragraph 21 wherein said elastomer        particles comprise about 62 volume % to about 78 volume %.        28. The process according to paragraph 21 wherein said elastomer        particles comprise about 62 volume % to about 76 volume %.        29. The process according to paragraph 21 wherein said degree of        cure is selected from the group consisting of about 60% to        greater than about 95%; about 65% to about 95%; about 70% to        about 95%; about 75% to greater than about 90%; about 80% to        about 98%; about 85% to about 95%; and about 85% to about 99%.        30. The process according to paragraph 21 wherein said degree of        cure is at least about 80%.        31. The process according to paragraph 21 wherein said elastomer        containing composition further comprises at least one component        selected from the group consisting of fillers and plasticizers.        32. The process according to paragraph 21 wherein said nylon        resin comprises a mixture of (i) nylon 11 or nylon 12; and (ii)        nylon 6/66 copolymer, and a composition ratio of (i)/(ii) is        about 10/90 to about 90/10.        33. The process according to paragraph 32 wherein said        composition ratio of (i)/(ii) is about 30/70 to about 85/15.        34. The process according to paragraph 21 wherein said at least        one halogenated isobutylene-containing elastomer is selected        from the group consisting of halogenated butyl rubber,        halogenated isoolefin/para-alkylstyrene copolymer, halogenated        isobutylene-p-methylstyrene-isoprene copolymer, halogenated        branched butyl rubber and halogenated star-branched butyl        rubber.        35. The process according to paragraph 34 wherein said        halogenated butyl rubber halogenated butyl rubber comprises a        high content of the following halogenated structure, where X        represents a halogen:

36. The process according to paragraph 34 or paragraph 35 wherein thehalogen is selected from the group consisting of bromine and chlorine.37. The process according to paragraph 34 wherein said halogenatedisoolefin/para-alkylstyrene copolymer copolymers comprises a C₄ to C₇isoolefin.38. The process according to paragraph 37 wherein said halogenatedisoolefin/para-alkylstyrene copolymer comprises a halogenatedpoly(isobutylene-co-p-methylstyrene) copolymer.39. The process according to paragraph 38 wherein said halogen isbromine.

1. A thermoplastic elastomer composition comprising (A) at least onehalogenated isobutylene-containing elastomer; and (B) at least one nylonresin having a melting point of about 170° C. to about 230° C.; wherein:(1) said at least one halogenated isobutylene-containing elastomer ispresent as a dispersed phase of small vulcanized or partially vulcanizedparticles in a continuous phase of said nylon; (2) said halogenatedisobutylene-containing elastomer particles have been formed by dynamicvulcanization; and (3) said halogenated isobutylene-containing elastomerparticles comprising greater than about 60 volume % of the volume ofsaid elastomer and said resin being obtained by a process comprising thesteps of: (1) mixing halogenated elastomer-containing composition (A′)comprising a first fraction of the total amount of halogenated elastomerin said thermoplastic elastomer composition and further comprising acure system for said first elastomer fraction; and thermoplastic nylonresin (B) under suitable dynamic vulcanization conditions of time,temperature and shear to form composition (C); (2) mixing composition(C) and halogenated elastomer-containing composition (D), saidcomposition (D) comprising a second fraction of the total amount ofhalogenated elastomer in said thermoplastic elastomer composition andfurther comprising a cure system for said second elastomer fraction;under suitable dynamic vulcanization conditions of time, temperature andshear to form composition (E); (3) if the sum of said first and secondfractions of halogenated elastomer is less than the total amount ofhalogenated elastomer in said thermoplastic elastomer composition,mixing composition (E) and halogenated elastomer-containing composition(F), said composition (F) comprising a third fraction of the totalamount of halogenated elastomer in said thermoplastic elastomercomposition and further comprising a cure system for said thirdelastomer fraction; under suitable dynamic vulcanization conditions oftime, temperature and shear to form composition (G); wherein the step ofdynamically vulcanizing a fractional additional amount of halogenatedelastomer in the presence of the dynamically vulcanized composition ofthe preceding step is repeated as many times as necessary in order toobtain the total amount of halogenated elastomer in said thermoplasticelastomer composition; and wherein each said dynamic vulcanizationconditions at each step are sufficient to effect a cure state in saidelastomer particles of at least about 50% of the maximum cure state forsaid elastomer and cure system and wherein said dynamic vulcanizationtime period is equal to or less than about the characteristic residencetime of said mixer.
 2. The composition according to claim 1 wherein saidelastomer particles are present in an amount of greater than 60 volume %to 80 volume %.
 3. The composition according to claim 1 wherein thedegree of cure of said elastomer particles is at least about 50% of themaximum degree of cure that said elastomer is capable of reaching basedon the composition and conditions under which said elastomer isvulcanized.
 4. The composition according to claim 1 wherein said nylonresin comprises a mixture of (i) nylon 11 or nylon 12; and (ii) nylon6/66 copolymer, and a composition ratio of (i)/(ii) is about 10/90 toabout 90/10.
 5. The composition according to claim 1 wherein said atleast one halogenated isobutylene-containing elastomer is selected fromthe group consisting of halogenated butyl rubber, halogenatedisobutylene/para-alkylstyrene copolymer, halogenatedisobutylene-p-methylstyrene-isoprene copolymer, halogenated branchedbutyl rubber and halogenated star-branched butyl rubber.
 6. Thecomposition according to claim 5 wherein said at least one halogenatedisobutylene-containing elastomer comprises a halogenatedisobutylene/para-alkylstyrene copolymer.
 7. The composition according toclaim 1 wherein said halogenated butyl rubber comprises a high contentof the following halogenated structure,

where X represents a halogen.
 8. The composition according to claim 7wherein the halogen is selected from the group consisting of bromine andchlorine.
 9. The composition of claim 1, the composition beingincorporated into an article, the article being an air permeationprevention layer of a pneumatic tire or a layer of a hose material. 10.A process conducted in a mixer for producing a thermoplastic elastomercomposition, said mixer having a characteristic residence time, saidcomposition comprising greater than about 60 volume % of dispersedparticles of a total amount of at least one halogenatedisobutylene-containing elastomer, said particles dispersed in acontinuous thermoplastic nylon resin matrix, said process comprising thesteps of: (1) mixing halogenated elastomer-containing composition (A′),said composition (A′) comprising a first fraction of the total amount ofhalogenated elastomer in said thermoplastic elastomer composition andfurther comprising a cure system for said first elastomer fraction; andthermoplastic nylon resin (B) under suitable dynamic vulcanizationconditions of time, temperature and shear to form composition (C); (2)mixing composition (C) and halogenated elastomer-containing composition(D), said composition (D) comprising a second fraction of the totalamount of halogenated elastomer in said thermoplastic elastomercomposition and further comprising a cure system for said secondelastomer fraction; under suitable dynamic vulcanization conditions oftime, temperature and shear to form composition (E); (3) if the sum ofsaid first and second fractions of halogenated elastomer is less thanthe total amount of halogenated elastomer in said thermoplasticelastomer composition, mixing composition (E) and halogenatedelastomer-containing composition (F), said composition (F) comprising athird fraction of the total amount of halogenated elastomer in saidthermoplastic elastomer composition and further comprising a cure systemfor said third elastomer fraction; under suitable dynamic vulcanizationconditions of time, temperature and shear to form composition (G);wherein the step of dynamically vulcanizing a fractional additionalamount of halogenated elastomer in the presence of the dynamicallyvulcanized composition of the preceding step is repeated as many timesas necessary in order to obtain the total amount of halogenatedelastomer in said thermoplastic elastomer composition; and wherein eachsaid dynamic vulcanization conditions at each step are sufficient toeffect a cure state in said elastomer particles of at least about 50% ofthe maximum cure state for said elastomer and cure system and whereinsaid dynamic vulcanization time period is equal to or less than aboutthe characteristic residence time of said mixer.
 11. The processaccording to claim 10 comprising two fractional additions of saidhalogenated elastomer.
 12. The process according to claim 10 comprisingat least three fractional additions of said halogenated elastomer. 13.The process according to claim 10 wherein said elastomer particles arepresent in an amount of greater than about 60 volume % to about 80volume %.
 14. The process according to claim 10, wherein said degree ofcure is about 60% to about 99%.
 15. The process according to claim 10,wherein said nylon resin comprises a mixture of (i) nylon 11 or nylon12; and (ii) nylon 6/66 copolymer, and a composition ratio of (i)/(ii)is about 10/90 to about 90/10.
 16. The process according to claim 10wherein said at least one halogenated isobutylene-containing elastomeris selected from the group consisting of halogenated butyl rubber,halogenated isobutylene/para-alkylstyrene copolymer, halogenatedisobutylene-p-methylstyrene-isoprene copolymer, halogenated branchedbutyl rubber and halogenated star-branched butyl rubber.
 17. The processaccording to claim 16 wherein said halogenated butyl rubber halogenatedbutyl rubber comprises a high content of the following halogenatedstructure,

where X represents a halogen.
 18. The process according to claim 17wherein the halogen is selected from the group consisting of bromine andchlorine.
 19. The process according to claim 16 wherein said at leastone halogenated isobutylene-containing elastomer comprises a halogenatedisobutylene/para-alkylstyrene copolymer.
 20. A thermoplastic elastomercomposition consisting essentially of a dynamically vulcanized mixtureof: (A) brominated isobutylene-p-methylstyrene elastomer; and (B) nylon6/66 copolymer resin; wherein said elastomer is present as a dispersedphase of small, dynamically vulcanized particles in a continuous phaseof said nylon and said elastomer particles comprise about 73 volume % ofthe volume of said elastomer and said resin; and wherein (1) saiddynamic vulcanization is conducted in two stages in a twin screwextruder having a residence time of about 1 minute; (2) using saidelastomer in which a cure system is previously dispersed, said curesystem exhibiting a cure time to at least 50% of maximum cure of theelastomer of less than said residence time of the extruder; (3) duringthe first stage of which a mixture of 55 weight percent Nylon and 45weight percent elastomer are dynamically vulcanized and during thesecond stage of which 70 parts by weight of the mixture produced in thefirst stage is further dynamically vulcanized with 30 parts by weight ofelastomer.